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/tools/env/fw_env.c b/tools/env/fw_env.c
index eef12dd..f06252d 100644
--- a/tools/env/fw_env.c
+++ b/tools/env/fw_env.c
@@ -10,6 +10,7 @@
 #define _GNU_SOURCE
 
 #include <compiler.h>
+#include <env.h>
 #include <errno.h>
 #include <env_flags.h>
 #include <fcntl.h>
diff --git a/tools/env/fw_env.h b/tools/env/fw_env.h
index b250e2f..3d2b457 100644
--- a/tools/env/fw_env.h
+++ b/tools/env/fw_env.h
@@ -4,6 +4,7 @@
  * Wolfgang Denk, DENX Software Engineering, wd@denx.de.
  */
 
+#include <env.h>
 #include <stdint.h>
 
 /*
diff --git a/tools/env/fw_env_main.c b/tools/env/fw_env_main.c
index 26ba662..1d193bd 100644
--- a/tools/env/fw_env_main.c
+++ b/tools/env/fw_env_main.c
@@ -26,6 +26,7 @@
  * of AES key), eg. '-a aabbccddeeff00112233445566778899'.
  */
 
+#include <env.h>
 #include <fcntl.h>
 #include <getopt.h>
 #include <stdio.h>