usb: gadget: UMS: Invoke board specific USB cleanup interface

This patch invokes board-specific USB cleanup (board_usb_cleanup)
function in the mass storage gadget

Signed-off-by: Inha Song <ideal.song@samsung.com>
diff --git a/common/cmd_usb_mass_storage.c b/common/cmd_usb_mass_storage.c
index 6cfee47..03f8be2 100644
--- a/common/cmd_usb_mass_storage.c
+++ b/common/cmd_usb_mass_storage.c
@@ -154,6 +154,7 @@
 	}
 exit:
 	g_dnl_unregister();
+	board_usb_cleanup(controller_index, USB_INIT_DEVICE);
 	return CMD_RET_SUCCESS;
 }