[gdb/testsuite] Fix gdb.tui/tui-layout-asm-short-prog.exp on cygwin

On x86_64-cygwin, I run into:
...
 Running tui-layout-asm-short-prog.exp ...
 gdb compile failed, tui-layout-asm-short-prog.S: Assembler messages:
 tui-layout-asm-short-prog.S:26: Error: \
   junk at end of line, first unrecognized character is `-'

                 === gdb Summary ===

 # of untested testcases         1
...

This is due to this note in gdb.tui/tui-layout-asm-short-prog.S:
...
        .section        .note.GNU-stack,"",@progbits
...

The note can be easily skipped for cygwin, but after doing so, we run into a
fail.

The problem is that while the test-case tries to generate 5 nops:
...
 	.rept 5
 	nop
 	.endr
...
in fact 16 nops are generated.

The fail is not specific to x86_64-cygwin, if we do ".rept 16" on
x86_64-linux, we get the same fail.

Fix this by increasing the "large" scroll amounts from 13 to 15.

Tested on x86_64-cygwin and x86_64-linux.
diff --git a/gdb/testsuite/gdb.tui/tui-layout-asm-short-prog.S b/gdb/testsuite/gdb.tui/tui-layout-asm-short-prog.S
index 9d69236..6e36152 100644
--- a/gdb/testsuite/gdb.tui/tui-layout-asm-short-prog.S
+++ b/gdb/testsuite/gdb.tui/tui-layout-asm-short-prog.S
@@ -20,8 +20,11 @@
 	.rept 5
 	nop
 	.endr
+
+#ifndef __CYGWIN__
 #ifdef __arm__
 	.section	.note.GNU-stack,"",%progbits
 #else
 	.section	.note.GNU-stack,"",@progbits
 #endif
+#endif
diff --git a/gdb/testsuite/gdb.tui/tui-layout-asm-short-prog.exp b/gdb/testsuite/gdb.tui/tui-layout-asm-short-prog.exp
index 23adbb0..e21914b 100644
--- a/gdb/testsuite/gdb.tui/tui-layout-asm-short-prog.exp
+++ b/gdb/testsuite/gdb.tui/tui-layout-asm-short-prog.exp
@@ -57,7 +57,7 @@
 
 # Scroll forward a large amount, this should take us to the last
 # instruction in the program.
-Term::command "+ 13"
+Term::command "+ 15"
 Term::check_box_contents "check asm box contents again" 0 0 80 15 \
     [multi_line \
 	 "^___$hex\[^\r\n\]+" \
@@ -65,6 +65,6 @@
 
 # Now scroll backward again, we should return to the start of the
 # program.
-Term::command "- 13"
+Term::command "- 15"
 gdb_assert {[string eq "$first_line" [Term::get_line 1]]} \
     "check first line is back"