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/drivers/usb/gadget/designware_udc.c b/drivers/usb/gadget/designware_udc.c
index fa947da..432f312 100644
--- a/drivers/usb/gadget/designware_udc.c
+++ b/drivers/usb/gadget/designware_udc.c
@@ -10,6 +10,7 @@
 #include <common.h>
 #include <asm/io.h>
 
+#include <env.h>
 #include <usbdevice.h>
 #include "ep0.h"
 #include <usb/designware_udc.h>
diff --git a/drivers/usb/gadget/f_dfu.c b/drivers/usb/gadget/f_dfu.c
index e27f146..6756155 100644
--- a/drivers/usb/gadget/f_dfu.c
+++ b/drivers/usb/gadget/f_dfu.c
@@ -14,6 +14,7 @@
  * (C) Copyright 2006 by Harald Welte <hwelte at hmw-consulting.de>
  */
 
+#include <env.h>
 #include <errno.h>
 #include <common.h>
 #include <malloc.h>
diff --git a/drivers/usb/gadget/f_fastboot.c b/drivers/usb/gadget/f_fastboot.c
index 3ad4346..fc27dbe 100644
--- a/drivers/usb/gadget/f_fastboot.c
+++ b/drivers/usb/gadget/f_fastboot.c
@@ -11,6 +11,7 @@
  */
 #include <config.h>
 #include <common.h>
+#include <env.h>
 #include <errno.h>
 #include <fastboot.h>
 #include <malloc.h>
diff --git a/drivers/usb/gadget/f_rockusb.c b/drivers/usb/gadget/f_rockusb.c
index f3d2477..1cfeabc 100644
--- a/drivers/usb/gadget/f_rockusb.c
+++ b/drivers/usb/gadget/f_rockusb.c
@@ -6,6 +6,7 @@
  */
 #include <config.h>
 #include <common.h>
+#include <env.h>
 #include <errno.h>
 #include <malloc.h>
 #include <memalign.h>