panic: hide unused global functions

Building with W=1 shows warnings about two functions that have no
declaration or caller in certain configurations:

kernel/panic.c:688:6: error: no previous prototype for 'warn_slowpath_fmt' [-Werror=missing-prototypes]
kernel/panic.c:710:6: error: no previous prototype for '__warn_printk' [-Werror=missing-prototypes]

Enclose the definition in the same #ifdef check as the declaration.

Link: https://lkml.kernel.org/r/20230517131102.934196-8-arnd@kernel.org
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Cc: Boqun Feng <boqun.feng@gmail.com>
Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: Christoph Lameter <cl@linux.com>
Cc: Dennis Zhou <dennis@kernel.org>
Cc: Eric Paris <eparis@redhat.com>
Cc: Heiko Carstens <hca@linux.ibm.com>
Cc: Helge Deller <deller@gmx.de>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Michael Ellerman <mpe@ellerman.id.au>
Cc: Michal Simek <monstr@monstr.eu>
Cc: Palmer Dabbelt <palmer@dabbelt.com>
Cc: Paul Moore <paul@paul-moore.com>
Cc: Pavel Machek <pavel@ucw.cz>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Rafael J. Wysocki <rafael@kernel.org>
Cc: Russell King <linux@armlinux.org.uk>
Cc: Tejun Heo <tj@kernel.org>
Cc: Thomas Bogendoerfer <tsbogend@alpha.franken.de>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Waiman Long <longman@redhat.com>
Cc: Will Deacon <will@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

kernel/panic.c

@@ -684,6 +684,7 @@ void __warn(const char *file, int line, void *caller, unsigned taint,
 	add_taint(taint, LOCKDEP_STILL_OK);
 }
 
+#ifdef CONFIG_BUG
 #ifndef __WARN_FLAGS
 void warn_slowpath_fmt(const char *file, int line, unsigned taint,
 		       const char *fmt, ...)
@@ -722,8 +723,6 @@ void __warn_printk(const char *fmt, ...)
 EXPORT_SYMBOL(__warn_printk);
 #endif
 
-#ifdef CONFIG_BUG
-
 /* Support resetting WARN*_ONCE state */
 
 static int clear_warn_once_set(void *data, u64 val)