kmemcheck: add missing braces to do-while in kmemcheck_annotate_bitfield

Whether or not the sparse warning

	warning: do-while statement is not a compound statement

is justified or not in this case, it is annoying and trivial to fix.

[vegard.nossum@gmail.com: title and cleanup]
Signed-off-by: Johannes Berg <johannes@sipsolutions.net>
Signed-off-by: Vegard Nossum <vegard.nossum@gmail.com>

include/linux/kmemcheck.h

@@ -137,7 +137,10 @@ static inline void kmemcheck_mark_initialized_pages(struct page *p,
 	int name##_end[0];
 
 #define kmemcheck_annotate_bitfield(ptr, name)				\
-	do if (ptr) {							\
+	do {								\
+		if (!ptr)						\
+			break;						\
+									\
 		int _n = (long) &((ptr)->name##_end)			\
 			- (long) &((ptr)->name##_begin);		\
 		BUILD_BUG_ON(_n < 0);					\