env: Move env_init() to env.h

Move env_init() over to the new header file.

Signed-off-by: Simon Glass <sjg@chromium.org>
Acked-by: Joe Hershberger <joe.hershberger@ni.com>
diff --git a/board/liebherr/display5/spl.c b/board/liebherr/display5/spl.c
index 27f843e..d92760b 100644
--- a/board/liebherr/display5/spl.c
+++ b/board/liebherr/display5/spl.c
@@ -5,6 +5,7 @@
  */
 
 #include <common.h>
+#include <env.h>
 #include <spl.h>
 #include <linux/libfdt.h>
 #include <asm/io.h>