One data channel is one data line. From imx7ulp, the SAI IP is
enhanced to support multiple data channels.

If there is only two channels input and slots is 2, then enable one
data channel is enough for data transfer. So enable the TCE/RCE and
transmit/receive mask register according to the input channels and
slots configuration.

Move the data channel enablement from startup() to hw_params().
Signed-off-by: Shengjiu Wang <shengjiu.wang@nxp.com>
Acked-by: Nicolin Chen <nicoleotsuka@gmail.com>
Link: https://lore.kernel.org/r/1598958068-10552-1-git-send-email-shengjiu.wang@nxp.comSigned-off-by: Mark Brown <broonie@kernel.org>