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/hisilicon/hikey/hikey.c b/board/hisilicon/hikey/hikey.c
index 28f5cf7..8440009 100644
--- a/board/hisilicon/hikey/hikey.c
+++ b/board/hisilicon/hikey/hikey.c
@@ -4,6 +4,7 @@
  * Peter Griffin <peter.griffin@linaro.org>
  */
 #include <common.h>
+#include <cpu_func.h>
 #include <dm.h>
 #include <fdt_support.h>
 #include <dm/platform_data/serial_pl01x.h>