usb: gadget: uvc: Only halt video streaming endpoint in bulk mode

[ Upstream commit 8dbf9c7abefd5c1434a956d5c6b25e11183061a3 ]

When USB requests for video data fail to be submitted, the driver
signals a problem to the host by halting the video streaming endpoint.
This is only valid in bulk mode, as isochronous transfers have no
handshake phase and can't thus report a stall. The usb_ep_set_halt()
call returns an error when using isochronous endpoints, which we happily
ignore, but some UDCs complain in the kernel log. Fix this by only
trying to halt the endpoint in bulk mode.

Signed-off-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Reviewed-by: Paul Elder <paul.elder@ideasonboard.com>
Tested-by: Paul Elder <paul.elder@ideasonboard.com>
Reviewed-by: Kieran Bingham <kieran.bingham@ideasonboard.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>