panic: suppress gnu_printf warning

with GCC 13.2.1 and W=1, there's compiling warning like this:

kernel/panic.c: In function `__warn':
kernel/panic.c:676:17: warning: function `__warn' might be a candidate for `gnu_printf' format attribute [-Wsuggest-attribute=format]
  676 |                 vprintk(args->fmt, args->args);
      |                 ^~~~~~~

The normal __printf(x,y) adding can't fix it. So add workaround which
disables -Wsuggest-attribute=format to mute it.

Link: https://lkml.kernel.org/r/20240107091641.579849-1-bhe@redhat.com
Signed-off-by: Baoquan He <bhe@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>