ext4: use swap() in memswap()

Use kernel.h macro definition.

Thanks to Julia Lawall for Coccinelle scripting support.
Signed-off-by: NFabian Frederick <fabf@skynet.be>
Signed-off-by: NTheodore Ts'o <tytso@mit.edu>

fs/ext4/ioctl.c

@@ -31,14 +31,11 @@
 static void memswap(void *a, void *b, size_t len)
 {
 	unsigned char *ap, *bp;
-	unsigned char tmp;
 
 	ap = (unsigned char *)a;
 	bp = (unsigned char *)b;
 	while (len-- > 0) {
-		tmp = *ap;
-		*ap = *bp;
-		*bp = tmp;
+		swap(*ap, *bp);
 		ap++;
 		bp++;
 	}