common: Move reset_cpu() to the CPU header

Move this function out of common.h and into a relevant header file.

Signed-off-by: Simon Glass <sjg@chromium.org>
diff --git a/arch/arm/mach-keystone/ddr3.c b/arch/arm/mach-keystone/ddr3.c
index 863ae63..23ff064 100644
--- a/arch/arm/mach-keystone/ddr3.c
+++ b/arch/arm/mach-keystone/ddr3.c
@@ -6,6 +6,7 @@
  *     Texas Instruments Incorporated, <www.ti.com>
  */
 
+#include <cpu_func.h>
 #include <asm/io.h>
 #include <common.h>
 #include <asm/arch/msmc.h>