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/board/udoo/udoo.c b/board/udoo/udoo.c
index c34a5a6..f2c2bf4 100644
--- a/board/udoo/udoo.c
+++ b/board/udoo/udoo.c
@@ -8,6 +8,7 @@
 #include <asm/arch/clock.h>
 #include <asm/arch/imx-regs.h>
 #include <asm/arch/iomux.h>
+#include <env.h>
 #include <malloc.h>
 #include <asm/arch/mx6-pins.h>
 #include <linux/errno.h>