ASoC: tlv320dac33: Fix inconsistent spinlock usage

The lock is used within the interrupt handler.
Correct the spinlock usage, and use irqsave/irqrestore
flavour of spin_lock/unlock.

Signed-off-by: Peter Ujfalusi <peter.ujfalusi@nokia.com>
Acked-by: Mark Brown <broonie@opensource.wolfsonmicro.com>
Signed-off-by: Liam Girdwood <lrg@slimlogic.co.uk>