ASoC: kirkwood-dma: don't ignore other irq causes on error

Ignoring the real cause of the interrupt is not a good idea; this
behaviour has been observed to bring Dove platforms to silently
lockup.  Instead, on error fall through to the normal interrupt
processing.

This is especially important on Dove platforms as errors are
handled separately, and allows us to clear down the real cause of
the interrupt.

Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>
Signed-off-by: Mark Brown <broonie@opensource.wolfsonmicro.com>