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/cpu/arm926ejs/mxs/mxs.c b/arch/arm/cpu/arm926ejs/mxs/mxs.c
index 183aa40..f44205c 100644
--- a/arch/arm/cpu/arm926ejs/mxs/mxs.c
+++ b/arch/arm/cpu/arm926ejs/mxs/mxs.c
@@ -10,6 +10,7 @@
  */
 
 #include <common.h>
+#include <cpu_func.h>
 #include <linux/errno.h>
 #include <asm/io.h>
 #include <asm/arch/clock.h>