ASoC: fsl-asoc-card: Add slot_width setting for cpu-dai

ESAI may need to use fixed slot width to comply with external
CODEC. So this set_tdm_slot() call will allow the ESAI driver
to override its default dynamic slot width policy.

Signed-off-by: Nicolin Chen <nicoleotsuka@gmail.com>
Signed-off-by: Mark Brown <broonie@kernel.org>