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-kirkwood/cpu.c b/arch/arm/mach-kirkwood/cpu.c
index 29c0e59..5e964af 100644
--- a/arch/arm/mach-kirkwood/cpu.c
+++ b/arch/arm/mach-kirkwood/cpu.c
@@ -7,6 +7,7 @@
 
 #include <common.h>
 #include <command.h>
+#include <cpu_func.h>
 #include <env.h>
 #include <netdev.h>
 #include <asm/cache.h>