FROMGIT: usb: gadget: uvc: set req_length based on payload by nreqs instead of req_size

Compressed formats generate content depending amount of data that is set
in the vb2 buffer by the payload_size. When streaming those formats it
is better to scatter that smaller data over all requests. This patch is
doing that by introducing the calculated req_payload_size which is
updated by each frame. It the uses this amount of data to fill the
isoc requests instead of the video->req_size.

For uncompressed formats it will not make a difference since the payload
size will be equal to the imagesize. Therefore the code will have no
effecta as req_payload_size will be equal to req_size.

Signed-off-by: Michael Grzeschik <m.grzeschik@pengutronix.de>
Link: https://lore.kernel.org/r/20240403-uvc_request_length_by_interval-v7-6-e224bb1035f0@pengutronix.de


Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

Bug: 379236348
(cherry picked from commit 98ad0329 https://git.kernel.org/pub/scm/linux/kernel/git/gregkh/usb.git/

 usb-next)
Change-Id: I6548070cbb8b797b868a288d104ebca72762b818
Signed-off-by: Selvarasu Ganesan <selvarasu.g@samsung.com>