usb: gadget: f_loopback: add configfs support

Add support for using the loopback USB function in gadgets composed with
configfs.

Signed-off-by: Andrzej Pietrasiewicz <andrzej.p@samsung.com>
Signed-off-by: Kyungmin Park <kyungmin.park@samsung.com>
Signed-off-by: Felipe Balbi <balbi@ti.com>
diff --git a/drivers/usb/gadget/zero.c b/drivers/usb/gadget/zero.c
index 0dd07ae..d954bba 100644
--- a/drivers/usb/gadget/zero.c
+++ b/drivers/usb/gadget/zero.c
@@ -66,8 +66,8 @@
 static struct usb_zero_options gzero_options = {
 	.isoc_interval = 4,
 	.isoc_maxpacket = 1024,
-	.bulk_buflen = 4096,
-	.qlen = 32,
+	.bulk_buflen = GZERO_BULK_BUFLEN,
+	.qlen = GZERO_QLEN,
 };
 
 /*-------------------------------------------------------------------------*/