ASoC: remove trigger delay in Freescale MPC8610 sound driver

Remove the delay from the trigger function in the Freescale MPC8610 sound
driver when capture is started.  This delay was used to ensure that the DMA
controller was active when ALSA call the .pointer function to request a
DMA transfer status.  A better approach is for the .pointer function to detect
that DMA has not started, and return zero instead.  This change eliminates
the need for the delay.

Also add some related code to check for a DMA programming error, and report
XRUN if it occurs.

Signed-off-by: Timur Tabi <timur@freescale.com>
Signed-off-by: Mark Brown <broonie@opensource.wolfsonmicro.com>