i386-fbsd-nat: Assume PT_GETXMMREGS is present.

PT_GETXMMREGS was first added in FreeBSD 6.0 released in November 2005.
The last FreeBSD release without support was 5.5 released in May 2006.
diff --git a/gdb/i386-fbsd-nat.c b/gdb/i386-fbsd-nat.c
index 6fb6743..a6ced66 100644
--- a/gdb/i386-fbsd-nat.c
+++ b/gdb/i386-fbsd-nat.c
@@ -42,9 +42,7 @@ class i386_fbsd_nat_target final
   void fetch_registers (struct regcache *, int) override;
   void store_registers (struct regcache *, int) override;
 
-#if defined(PT_GETXMMREGS) || defined(PT_GETXSTATE_INFO)
   const struct target_desc *read_description () override;
-#endif
 
   void resume (ptid_t, int, enum gdb_signal) override;
 
@@ -59,9 +57,7 @@ static i386_fbsd_nat_target the_i386_fbsd_nat_target;
 static size_t xsave_len;
 #endif
 
-#ifdef HAVE_PT_GETXMMREGS
 static int have_ptrace_xmmregs;
-#endif
 
 /* Fetch register REGNUM from the inferior.  If REGNUM is -1, do this
    for all registers.  */
@@ -126,7 +122,6 @@ i386_fbsd_nat_target::fetch_registers (struct regcache *regcache, int regnum)
       return;
     }
 #endif
-#ifdef HAVE_PT_GETXMMREGS
   if (have_ptrace_xmmregs != 0)
     {
       char xmmregs[I387_SIZEOF_FXSAVE];
@@ -137,7 +132,6 @@ i386_fbsd_nat_target::fetch_registers (struct regcache *regcache, int regnum)
       i387_supply_fxsave (regcache, regnum, xmmregs);
       return;
     }
-#endif
 
   struct fpreg fpregs;
 
@@ -214,7 +208,6 @@ i386_fbsd_nat_target::store_registers (struct regcache *regcache, int regnum)
       return;
     }
 #endif
-#ifdef HAVE_PT_GETXMMREGS
   if (have_ptrace_xmmregs != 0)
     {
       char xmmregs[I387_SIZEOF_FXSAVE];
@@ -228,7 +221,6 @@ i386_fbsd_nat_target::store_registers (struct regcache *regcache, int regnum)
 	perror_with_name (_("Couldn't write XMM registers"));
       return;
     }
-#endif
 
   struct fpreg fpregs;
 
@@ -324,7 +316,6 @@ i386fbsd_supply_pcb (struct regcache *regcache, struct pcb *pcb)
 }
 
 
-#if defined(PT_GETXMMREGS) || defined(PT_GETXSTATE_INFO)
 /* Implement the read_description method.  */
 
 const struct target_desc *
@@ -334,9 +325,7 @@ i386_fbsd_nat_target::read_description ()
   static int xsave_probed;
   static uint64_t xcr0;
 #endif
-#ifdef PT_GETXMMREGS
   static int xmm_probed;
-#endif
 
 #ifdef PT_GETXSTATE_INFO
   if (!xsave_probed)
@@ -356,7 +345,6 @@ i386_fbsd_nat_target::read_description ()
     return i386_target_description (xcr0, true);
 #endif
 
-#ifdef PT_GETXMMREGS
   if (!xmm_probed)
     {
       char xmmregs[I387_SIZEOF_FXSAVE];
@@ -369,11 +357,9 @@ i386_fbsd_nat_target::read_description ()
 
   if (have_ptrace_xmmregs)
     return i386_target_description (X86_XSTATE_SSE_MASK, true);
-#endif
 
   return i386_target_description (X86_XSTATE_X87_MASK, true);
 }
-#endif
 
 #if defined(HAVE_PT_GETDBREGS) && defined(USE_SIGTRAP_SIGINFO)
 /* Implement the supports_stopped_by_hw_breakpoints method.  */