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-imx8/apalis-imx8.c b/board/toradex/apalis-imx8/apalis-imx8.c
index 0483041..fdfab8f 100644
--- a/board/toradex/apalis-imx8/apalis-imx8.c
+++ b/board/toradex/apalis-imx8/apalis-imx8.c
@@ -4,6 +4,7 @@
  */
 
 #include <common.h>
+#include <cpu_func.h>
 #include <init.h>
 
 #include <asm/arch/clock.h>