ARM/Samsung: be able to include the nand header multiple times

This is required in preparation for the following patches.

Signed-off-by: Juergen Beisert <jbe@pengutronix.de>

arch/arm/mach-samsung/include/mach/s3c24xx-nand.h

@@ -18,6 +18,9 @@
  *
  */
 
+#ifndef MACH_S3C24XX_NAND_H
+# define MACH_S3C24XX_NAND_H
+
 #ifdef CONFIG_S3C_NAND_BOOT
 extern void s3c24x0_nand_load_image(void*, int, int);
 #endif
@@ -52,3 +55,5 @@ struct s3c24x0_nand_platform_data {
  * @file
  * @brief Basic declaration to use the s3c24x0 NAND driver
  */
+
+#endif /* MACH_S3C24XX_NAND_H */