gcc-4.6: pagemap: avoid unused-but-set variable

Avoid quite a lot of warnings in header files in a gcc 4.6 -Wall builds
Signed-off-by: Andi Kleen <ak@linux.intel.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

include/linux/pagemap.h

@@ -423,8 +423,10 @@ static inline int fault_in_pages_readable(const char __user *uaddr, int size)
 		const char __user *end = uaddr + size - 1;
 
 		if (((unsigned long)uaddr & PAGE_MASK) !=
-				((unsigned long)end & PAGE_MASK))
+				((unsigned long)end & PAGE_MASK)) {
 		 	ret = __get_user(c, end);
+			(void)c;
+		}
 	}
 	return ret;
 }