vsnprintf: Silence false positive GCC warning for va_format()

va_format() is using vsnprintf(), and GCC compiler (Debian 14.2.0-17)
is not happy about this:

lib/vsprintf.c:1704:9: error: function ‘va_format’ might be a candidate for ‘gnu_print ’ format attribute [-Werror=suggest-attribute=format]

Fix the compilation errors (`make W=1` when CONFIG_WERROR=y, which is default)
by silencing the false positive GCC warning.

Suggested-by: Rasmus Villemoes <ravi@prevas.dk>
Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Reviewed-by: Kees Cook <kees@kernel.org>
Reviewed-by: Petr Mladek <pmladek@suse.com>
Link: https://lore.kernel.org/r/20250321144822.324050-7-andriy.shevchenko@linux.intel.com
Signed-off-by: Petr Mladek <pmladek@suse.com>

Author: andy-shev

lib/vsprintf.c

@@ -1699,6 +1699,10 @@ char *escaped_string(char *buf, char *end, u8 *addr, struct printf_spec spec,
 	return buf;
 }
 
+#pragma GCC diagnostic push
+#ifndef __clang__
+#pragma GCC diagnostic ignored "-Wsuggest-attribute=format"
+#endif
 static char *va_format(char *buf, char *end, struct va_format *va_fmt,
 		       struct printf_spec spec)
 {
@@ -1713,6 +1717,7 @@ static char *va_format(char *buf, char *end, struct va_format *va_fmt,
 
 	return buf;
 }
+#pragma GCC diagnostic pop
 
 static noinline_for_stack
 char *uuid_string(char *buf, char *end, const u8 *addr,