env: Move env_set() to env.h

Move env_set() over to the new header file.

Acked-by: Joe Hershberger <joe.hershberger@ni.com>
Signed-off-by: Simon Glass <sjg@chromium.org>
diff --git a/arch/arm/mach-rmobile/cpu_info.c b/arch/arm/mach-rmobile/cpu_info.c
index dc407d2..9ef94a4 100644
--- a/arch/arm/mach-rmobile/cpu_info.c
+++ b/arch/arm/mach-rmobile/cpu_info.c
@@ -5,6 +5,7 @@
  */
 #include <common.h>
 #include <asm/io.h>
+#include <env.h>
 #include <linux/ctype.h>
 
 #ifdef CONFIG_ARCH_CPU_INIT