ASoC: TWL4030: Add 4 channel TDM support

Support for 4 channel TDM (SND_SOC_DAIFMT_DSP_A) for twl4030
codec.
The channel allocations are:
Playback:
TDM         i2s   TWL RX
Channel 1   Left  SDRL2
Channel 3   Right SDRR2
Channel 2   --    SDRL1
Channel 4   --    SDRR1

Capture:
TDM         i2s   TWL TX
Channel 1   Left  TXL1
Channel 3   Right TXR1
Channel 2   --    TXL2
Channel 4   --    TXR2

Signed-off-by: Peter Ujfalusi <peter.ujfalusi@nokia.com>
Signed-off-by: Mark Brown <broonie@opensource.wolfsonmicro.com>