ASoC: omap-mcpdm: Replace legacy driver

Reasons for the replacement:
The current driver for McPDM was developed to support the legacy mode only.
In preparation for the ABE support the current driver stack need the be
replaced.
The new driver is much simpler, easier to extend, and it also fixes some of the
issues with the old stack.

Main changes:
- single file for omap-mcpdm (mcpdm.c/h removed)
- Define names for registers, bits cleaned up, prefixed
- Full-duplex audio operation (arecord | aplay) has been fixed
- Less code

McPDM need to be turned off after all streams has been stopped.
This might cause pop noise on the output, if the codec's DAC is
still powered at this time.

Signed-off-by: Misael Lopez Cruz <misael.lopez@ti.com>
Signed-off-by: Liam Girdwood <lrg@ti.com>
Signed-off-by: Sebastien Guiriec <s-guiriec@ti.com>
Signed-off-by: Peter Ujfalusi <peter.ujfalusi@ti.com>
Acked-by: Mark Brown <broonie@opensource.wolfsonmicro.com>