media: uvcvideo: fix division by zero at stream start

Add the missing bulk-endpoint max-packet sanity check to
uvc_video_start_transfer() to avoid division by zero in
uvc_alloc_urb_buffers() in case a malicious device has broken
descriptors (or when doing descriptor fuzz testing).

Note that USB core will reject URBs submitted for endpoints with zero
wMaxPacketSize but that drivers doing packet-size calculations still
need to handle this (cf. commit 2548288b ("USB: Fix: Don't skip
endpoint descriptors with maxpacket=0")).

Fixes: c0efd232 ("V4L/DVB (8145a): USB Video Class driver")
Cc: stable@vger.kernel.org      # 2.6.26
Signed-off-by: Johan Hovold <johan@kernel.org>
Reviewed-by: Kieran Bingham <kieran.bingham+renesas@ideasonboard.com>
Signed-off-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab+huawei@kernel.org>