kernel.h: remove initialization of bool in printk_once

Don't initialize __print_once.  Invert the test to reduce initialized
data.

defconfig before:	$size vmlinux
   text	   data	    bss	    dec	    hex	filename
6976022	 679572	1359668	9015262	 898fde	vmlinux

defconfig after:	$size vmlinux
   text	   data	    bss	    dec	    hex	filename
6976006	 679508	1359700	9015214	 898fae	vmlinux
Signed-off-by: Joe Perches <joe@perches.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

include/linux/kernel.h

@@ -251,10 +251,10 @@ extern int printk_delay_msec;
  * Print a one-time message (analogous to WARN_ONCE() et al):
  */
 #define printk_once(x...) ({			\
-	static bool __print_once = true;	\
+	static bool __print_once;		\
 						\
-	if (__print_once) {			\
-		__print_once = false;		\
+	if (!__print_once) {			\
+		__print_once = true;		\
 		printk(x);			\
 	}					\
 })