ASoC: omap-mcbsp: Clean up the interrupt handlers

The parameter name of dev_id is leftover from the old times when we passed
numeric ID as data for the interrupt handlers.

The mcbsp_rx and mcbsp_tx is misleading as they are pointers to the mcbsp
struct.

Signed-off-by: Peter Ujfalusi <peter.ujfalusi@ti.com>
Acked-by: Jarkko Nikula <jarkko.nikula@bitmer.com>
Tested-by: Jarkko Nikula <jarkko.nikula@bitmer.com>
Signed-off-by: Mark Brown <broonie@kernel.org>