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>

common/cli_hush.c

@@ -75,6 +75,7 @@
 
 #define __U_BOOT__
 #ifdef __U_BOOT__
+#include <env.h>
 #include <malloc.h>         /* malloc, free, realloc*/
 #include <linux/ctype.h>    /* isalpha, isdigit */
 #include <common.h>        /* readline */