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/tqc/tqma6/tqma6.c b/board/tqc/tqma6/tqma6.c
index 5f0c7aa..5b20afd 100644
--- a/board/tqc/tqma6/tqma6.c
+++ b/board/tqc/tqma6/tqma6.c
@@ -12,6 +12,7 @@
 #include <asm/arch/imx-regs.h>
 #include <asm/arch/iomux.h>
 #include <asm/arch/sys_proto.h>
+#include <env.h>
 #include <linux/errno.h>
 #include <asm/gpio.h>
 #include <asm/io.h>