bug: avoid format attribute warning for clang as well

Like gcc, clang-22 now also warns about a function that it incorrectly
identifies as a printf-style format:

lib/bug.c:190:22: error: diagnostic behavior may be improved by adding the 'format(printf, 1, 0)' attribute to the declaration of '__warn_printf' [-Werror,-Wmissing-format-attribute]
179 | static void __warn_printf(const char *fmt, struct pt_regs *regs)
| __attribute__((format(printf, 1, 0)))
180 | {
181 | if (!fmt)
182 | return;
183 |
184 | #ifdef HAVE_ARCH_BUG_FORMAT_ARGS
185 | if (regs) {
186 | struct arch_va_list _args;
187 | va_list *args = __warn_args(&_args, regs);
188 |
189 | if (args) {
190 | vprintk(fmt, *args);
| ^

Revert the change that added a gcc-specific workaround, and instead add
the generic annotation that avoid the warning.

Link: https://lkml.kernel.org/r/20260323205534.1284284-1-arnd@kernel.org
Fixes: d36067d6ea00 ("bug: Hush suggest-attribute=format for __warn_printf()")
Suggested-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Suggested-by: Brendan Jackman <jackmanb@google.com>
Link: https://lore.kernel.org/all/20251208141618.2805983-1-andriy.shevchenko@linux.intel.com/T/#u
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Reviewed-by: Brendan Jackman <jackmanb@google.com>
Reviewed-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Cc: Bill Wendling <morbo@google.com>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: Justin Stitt <justinstitt@google.com>
Cc: Nathan Chancellor <nathan@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>