media: imx-pxp: Pass pixel format value to find_format()

The find_format() function looks up format information for a given pixel
format. It takes a v4l2_format pointer, but only uses the contained
pixel format value. To prepare it for being used by callers that don't
have v4l2_format, modify it to take the pixel format value directly.

Signed-off-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Signed-off-by: Michael Tretter <m.tretter@pengutronix.de>
Reviewed-by: Philipp Zabel <p.zabel@pengutronix.de>
Signed-off-by: Mauro Carvalho Chehab <mchehab@kernel.org>