this patch make it more reasonable and readable, because when we chose
I2S_CKR_TRCM_TXONLY, we only output clk_lrck_tx, and hardware need to
confirm this signal is wired to external codec lrck_tx/rx at the same time.

for convenience, we just handle lrck_txonly if we enable symmetric_rates
in driver and dai_link. otherwise, we use the separate lrck_tx/rx.
Signed-off-by: Sugar Zhang <sugar.zhang@rock-chips.com>
Signed-off-by: Xing Zheng <zhengxing@rock-chips.com>
Signed-off-by: Mark Brown <broonie@kernel.org>