ASoC: rsnd: dma: set bus width to data width for monaural data

According to R-Car3 HW manual 40.3.3 (Data Format on Audio Local Bus),
in case of monaural data writing or reading through Audio-DMAC,
it's always in Left Justified format, so both src and dst
DMA Bus width should be equal to physical data width.

Therefore set src and dst's DMA bus width to:
 - [monaural case] data width
 - [non-monaural case] 32bits (as prior applying the patch)

Cc: Andrew Gabbasov <andrew_gabbasov@mentor.com>
Cc: Timo Wischer <twischer@de.adit-jv.com>
Signed-off-by: Jiada Wang <jiada_wang@mentor.com>
Signed-off-by: Eugeniu Rosca <erosca@de.adit-jv.com>
Link: https://lore.kernel.org/r/20191022185518.12838-1-erosca@de.adit-jv.com


Signed-off-by: Mark Brown <broonie@kernel.org>