WARN_ONCE(): use bool for boolean flag

Commit 70867453092297be9afb2249e712a1f960ec0a09 ("printk_once(): use bool
for boolean flag") changed printk_once() to use bool instead of int for
its guard variable.  Do the same change to WARN_ONCE() and WARN_ON_ONCE(),
for the same reasons.

This resulted in a reduction of 1462 bytes on a x86-64 defconfig:

   text    data     bss     dec     hex filename
8101271 1207116  992764 10301151         9d2edf vmlinux.before
8100553 1207148  991988 10299689         9d2929 vmlinux.after

Signed-off-by: Cesar Eduardo Barros <cesarb@cesarb.net>
Cc: Roland Dreier <rolandd@cisco.com>
Cc: Daniel Walker <dwalker@fifo99.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

include/asm-generic/bug.h

@@ -113,22 +113,22 @@ extern void warn_slowpath_null(const char *file, const int line);
 #endif
 
 #define WARN_ON_ONCE(condition)	({				\
-	static int __warned;					\
+	static bool __warned;					\
 	int __ret_warn_once = !!(condition);			\
 								\
 	if (unlikely(__ret_warn_once))				\
 		if (WARN_ON(!__warned)) 			\
-			__warned = 1;				\
+			__warned = true;			\
 	unlikely(__ret_warn_once);				\
 })
 
 #define WARN_ONCE(condition, format...)	({			\
-	static int __warned;					\
+	static bool __warned;					\
 	int __ret_warn_once = !!(condition);			\
 								\
 	if (unlikely(__ret_warn_once))				\
 		if (WARN(!__warned, format)) 			\
-			__warned = 1;				\
+			__warned = true;			\
 	unlikely(__ret_warn_once);				\
 })