ASoC: SPEAr spdif_{in,out}: use devm for clk and a few more cleanups

Drop dev_set_drvdata as this is handled in the core and use
devm_request_and_ioremap instead of devm_ioremap to properly register the
address range used

Signed-off-by: Uwe Kleine-König <u.kleine-koenig@pengutronix.de>
Signed-off-by: Mark Brown <broonie@opensource.wolfsonmicro.com>