usb, g_dnl: generalize DFU detach functions

In order to add detach functions for fastboot, make the DFU detach related
functions common so they can be shared.

Signed-off-by: Rob Herring <robh@kernel.org>
Tested-by: Lukasz Majewski <l.majewski@samsung.com>
[TestHW: Exynos4412-Trats2]
diff --git a/drivers/usb/gadget/f_dfu.c b/drivers/usb/gadget/f_dfu.c
index 16fc9dd..ead71eb 100644
--- a/drivers/usb/gadget/f_dfu.c
+++ b/drivers/usb/gadget/f_dfu.c
@@ -366,7 +366,7 @@
 		to_runtime_mode(f_dfu);
 		f_dfu->dfu_state = DFU_STATE_appIDLE;
 
-		dfu_trigger_detach();
+		g_dnl_trigger_detach();
 		break;
 	default:
 		f_dfu->dfu_state = DFU_STATE_dfuERROR;