arm: exynos: Include missing CPU header in soc.c

samsung_get_base_swreset() is called in soc.c, but corresponding header
with its prototype is not included. Fix this to avoid possible build
errors.

Signed-off-by: Sam Protsenko <semen.protsenko@linaro.org>
Signed-off-by: Minkyu Kang <mk7.kang@samsung.com>
diff --git a/arch/arm/mach-exynos/soc.c b/arch/arm/mach-exynos/soc.c
index a07c87a..6fe61cf 100644
--- a/arch/arm/mach-exynos/soc.c
+++ b/arch/arm/mach-exynos/soc.c
@@ -9,6 +9,7 @@
 #include <asm/cache.h>
 #include <asm/io.h>
 #include <asm/system.h>
+#include <asm/arch/cpu.h>
 
 #ifdef CONFIG_TARGET_ESPRESSO7420
 /*