gdb: Always suppress stringop-overread warning in debuginfod-support.c

gdb: Always suppress stringop-overread warning in debuginfod-support.c

Just like on s390x with g++ 11.2.1 and ppc64le with g++ 11.3.1 g++ 11
on hppa produces a spurious warning for stringop-overread in
debuginfod_is_enabled for url_view. Just always suppress it on all
arches.

https://sourceware.org/bugzilla/show_bug.cgi?id=29198

gdb/ChangeLog:

	* debuginfod-support.c (debuginfod_is_enabled): Always use
	DIAGNOSTIC_IGNORE_STRINGOP_OVERREAD.