gas: add missing header guard in tc-<arch>.h files

This patch adds missing header guards in some of the tc-<arch>.h,
and merely comments on the corresponding #endif for others. The
patch does not aim at being exhaustive, it only touched the files
relevant for [1].

[1]: https://inbox.sourceware.org/binutils/20250711112913.2453285-1-matthieu.longo@arm.com/
diff --git a/gas/config/tc-arc.h b/gas/config/tc-arc.h
index 145d955..65470f0 100644
--- a/gas/config/tc-arc.h
+++ b/gas/config/tc-arc.h
@@ -271,4 +271,4 @@
 extern void arc_md_end (void);
 #define md_end arc_md_end
 
-#endif
+#endif /* TC_ARC */
diff --git a/gas/config/tc-arm.h b/gas/config/tc-arm.h
index aa5f117..4148a6f 100644
--- a/gas/config/tc-arm.h
+++ b/gas/config/tc-arm.h
@@ -20,6 +20,7 @@
    Software Foundation, 51 Franklin Street - Fifth Floor, Boston, MA
    02110-1301, USA.  */
 
+#ifndef TC_ARM
 #define TC_ARM 1
 
 #ifndef TARGET_BYTES_BIG_ENDIAN
@@ -377,3 +378,5 @@
 #define TC_LARGEST_EXPONENT_IS_NORMAL(PRECISION) \
 	arm_is_largest_exponent_ok ((PRECISION))
 int arm_is_largest_exponent_ok (int precision);
+
+#endif /* TC_ARM */
diff --git a/gas/config/tc-csky.h b/gas/config/tc-csky.h
index 7e32347..d391084 100644
--- a/gas/config/tc-csky.h
+++ b/gas/config/tc-csky.h
@@ -106,4 +106,4 @@
 const char * elf32_csky_target_format (void);
 #endif
 
-#endif
+#endif /* TC_CSKY */
diff --git a/gas/config/tc-msp430.h b/gas/config/tc-msp430.h
index 47da4aa..fc39a59 100644
--- a/gas/config/tc-msp430.h
+++ b/gas/config/tc-msp430.h
@@ -20,6 +20,7 @@
    Software Foundation, 51 Franklin Street - Fifth Floor, Boston, MA
    02110-1301, USA.  */
 
+#ifndef TC_MSP430
 #define TC_MSP430
 /*   By convention, you should define this macro in the `.h' file.  For
      example, `tc-m68k.h' defines `TC_M68K'.  You might have to use this
@@ -172,3 +173,5 @@
 #define TC_LINKRELAX_FIXUP(seg) ((seg->flags & SEC_CODE) || (seg->flags & SEC_DEBUGGING))
 
 #define DWARF2_ADDR_SIZE(bfd) 4
+
+#endif /* TC_MSP430 */
diff --git a/gas/config/tc-ppc.h b/gas/config/tc-ppc.h
index 97e2f4e..e568c42 100644
--- a/gas/config/tc-ppc.h
+++ b/gas/config/tc-ppc.h
@@ -19,6 +19,7 @@
    Software Foundation, 51 Franklin Street - Fifth Floor, Boston, MA
    02110-1301, USA.  */
 
+#ifndef TC_PPC
 #define TC_PPC
 
 #include "opcode/ppc.h"
@@ -367,3 +368,5 @@
 #define DWARF2_DEFAULT_RETURN_COLUMN    0x41
 #define DWARF2_CIE_DATA_ALIGNMENT       ppc_cie_data_alignment
 #define EH_FRAME_ALIGNMENT		2
+
+#endif /* TC_PPC */
diff --git a/gas/config/tc-s390.h b/gas/config/tc-s390.h
index c92769e..0c62125 100644
--- a/gas/config/tc-s390.h
+++ b/gas/config/tc-s390.h
@@ -19,6 +19,7 @@
    Software Foundation, 51 Franklin Street - Fifth Floor, Boston, MA
    02110-1301, USA.  */
 
+#ifndef TC_S390
 #define TC_S390
 
 struct fix;
@@ -129,3 +130,5 @@
 /* The abi/arch identifier for SFrame.  */
 unsigned char s390_sframe_get_abi_arch (void);
 #define sframe_get_abi_arch s390_sframe_get_abi_arch
+
+#endif /* TC_S390 */
diff --git a/gas/config/tc-sparc.h b/gas/config/tc-sparc.h
index d569fe7..cfb89e0 100644
--- a/gas/config/tc-sparc.h
+++ b/gas/config/tc-sparc.h
@@ -178,4 +178,4 @@
    this, BFD_RELOC_32_PCREL will be emitted directly instead.  */
 #define CFI_DIFF_EXPR_OK 0
 
-#endif
+#endif /* TC_SPARC */
diff --git a/gas/config/tc-tic6x.h b/gas/config/tc-tic6x.h
index 55f2b2c..5859333 100644
--- a/gas/config/tc-tic6x.h
+++ b/gas/config/tc-tic6x.h
@@ -18,7 +18,9 @@
    Software Foundation, 51 Franklin Street - Fifth Floor, Boston, MA
    02110-1301, USA.  */
 
+#ifndef TC_TIC6X
 #define TC_TIC6X 1
+
 #define TARGET_BYTES_BIG_ENDIAN 0
 #define WORKING_DOT_WORD
 #define DOUBLEBAR_PARALLEL
@@ -225,3 +227,5 @@
 void tic6x_cfi_endproc (struct fde_entry *fde);
 
 #define tc_cfi_section_name ".c6xabi.exidx"
+
+#endif /* TC_TIC6X */