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-at91/arm926ejs/reset.c b/arch/arm/mach-at91/arm926ejs/reset.c
index 06b25db..56fbbd9 100644
--- a/arch/arm/mach-at91/arm926ejs/reset.c
+++ b/arch/arm/mach-at91/arm926ejs/reset.c
@@ -6,6 +6,7 @@
  */
 
 #include <common.h>
+#include <cpu_func.h>
 #include <asm/io.h>
 #include <asm/arch/hardware.h>
 #include <asm/arch/at91_rstc.h>