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/common/console.c b/common/console.c
index d086fea..0f7e091 100644
--- a/common/console.c
+++ b/common/console.c
@@ -8,6 +8,7 @@
 #include <console.h>
 #include <debug_uart.h>
 #include <dm.h>
+#include <env.h>
 #include <stdarg.h>
 #include <iomux.h>
 #include <malloc.h>