The UVC spec is a bit vague wrt devices using bulk endpoints,
specifically, how to signal to a device to start streaming.

For devices using isoc endpoints, the sequence for start streaming is:
1) The host sends PROBE_CONTROL(SET_CUR) PROBE_CONTROL(GET_CUR)
2) Host selects desired config and calls COMMIT_CONTROL(SET_CUR)
3) Host selects an alt interface other then zero - e.g SELECT_ALTERNATE_INTERFACE(1)
4) The device starts streaming

However for devices using bulk endpoints, there must be *no* alt interface
other than setting zero. From the UVC spec:
"A VideoStreaming interface containing a bulk endpoint for streaming shall
support only alternate setting zero. Additional alternate settings containing
bulk endpoints are not permitted in a device that is compliant with the Video
Class specification."

So for devices using bulk endpoints, step #3 above is irrelevant, and thus
cannot be used as an indication for the device to start streaming.
So in practice, such devices start streaming immediately after a
COMMIT_CONTROL(SET_CUR).

In the uvc resume() handler, an unsolicited commit is sent, which causes
devices using bulk endpoints to start streaming unintentionally.

This patch modifies resume() handler to send a commit only if streaming
needs to be reestablished, i.e if the device was actually streaming before is
was suspended.
Signed-off-by: Aviv Greenberg <aviv.d.greenberg@intel.com>
Signed-off-by: Guennadi Liakhovetski <g.liakhovetski@gmx.de>
Signed-off-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@osg.samsung.com>