omap: McBSP: Do not use extensive spin locks for dma_op_mode

The use of the spin lock, which supposed to protect the the
dma_op_mode causing "INFO: inconsistent lock state" on
playback start.
Remove the spin locks around the dma_op_mode, when it's
purpuse is to protect the dma_op_mode.

Signed-off-by: Peter Ujfalusi <peter.ujfalusi@nokia.com>
Acked-by: Jarkko Nikula <jhnikula@gmail.com>
Signed-off-by: Tony Lindgren <tony@atomide.com>