rtc-s3c: Use is_power_of_2() macro for simplicity.

Use is_power_of_2() macro for simplicity.
Signed-off-by: Robert P. J. Day <rpjday@crashcourse.ca>
Signed-off-by: Alessandro Zummo <a.zummo@towertech.it>
Cc: David Brownell <david-b@pacbell.net>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

drivers/rtc/rtc-s3c.c

@@ -20,6 +20,7 @@
 #include <linux/rtc.h>
 #include <linux/bcd.h>
 #include <linux/clk.h>
+#include <linux/log2.h>
 
 #include <asm/hardware.h>
 #include <asm/uaccess.h>
@@ -309,9 +310,7 @@ static int s3c_rtc_ioctl(struct device *dev,
 		break;
 
 	case RTC_IRQP_SET:
-		/* check for power of 2 */
-
-		if ((arg & (arg-1)) != 0 || arg < 1) {
+		if (!is_power_of_2(arg)) {
 			ret = -EINVAL;
 			goto exit;
 		}