ARM: SAMSUNG: fix to prevent declaring duplicated

The plat/clock.h revised to prevent declaring duplicated.
Signed-off-by: Kukjin Kim <kgene.kim@samsung.com>

arch/arm/plat-samsung/include/plat/clock.h

@@ -9,6 +9,9 @@
  * published by the Free Software Foundation.
 */
 
+#ifndef __ASM_PLAT_CLOCK_H
+#define __ASM_PLAT_CLOCK_H __FILE__
+
 #include <linux/spinlock.h>
 #include <linux/clkdev.h>
 
@@ -124,3 +127,5 @@ extern void s3c_pwmclk_init(void);
 /* Global watchdog clock used by arch_wtd_reset() callback */
 
 extern struct clk *s3c2410_wdtclk;
+
+#endif /* __ASM_PLAT_CLOCK_H */