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/board/toradex/apalis_imx6/apalis_imx6.c b/board/toradex/apalis_imx6/apalis_imx6.c
index d569782..3f85f1a 100644
--- a/board/toradex/apalis_imx6/apalis_imx6.c
+++ b/board/toradex/apalis_imx6/apalis_imx6.c
@@ -7,6 +7,7 @@
  */
 
 #include <common.h>
+#include <cpu_func.h>
 #include <dm.h>
 #include <init.h>