imx_dma_request_by_prio can return channel number by itself.
No need to supply variable address through parameters.

Also converted all drivers using this function.
Signed-off-by: NPaulius Zaleckas <paulius.zaleckas@teltonika.lt>
Acked-by: NSascha Hauer <s.hauer@pengutronix.de>
Signed-off-by: NRussell King <rmk+kernel@arm.linux.org.uk>