ASoC: rt722-sdca: modify channel number to support 4 channels

Channel numbers of dmic supports 4 channels, modify channels_max
regarding to this issue.

Signed-off-by: Jack Yu <jack.yu@realtek.com>
Link: https://msgid.link/r/6a9b1d1fb2ea4f04b2157799f04053b1@realtek.com


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