env: Move env_get() to env.h

Move env_get() 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/freescale/ls1088a/ls1088a.c b/board/freescale/ls1088a/ls1088a.c
index 6d11a13..a1c9eb3 100644
--- a/board/freescale/ls1088a/ls1088a.c
+++ b/board/freescale/ls1088a/ls1088a.c
@@ -3,6 +3,7 @@
  * Copyright 2017-2018 NXP
  */
 #include <common.h>
+#include <env.h>
 #include <i2c.h>
 #include <malloc.h>
 #include <errno.h>