ASoC: codecs: wcd938x: fix uninitialized symbol warnings

ASoC: codecs: wcd938x: fix uninitialized symbol warnings

This patch fixes below two uninitialized symbol warnings

warning:
	sound/soc/codecs/wcd938x.c:2092 wcd938x_tx_swr_ctrl()
	error: uninitialized symbol 'rate'

	sound/soc/codecs/wcd938x.c:2189 wcd938x_tx_channel_config()
	error: uninitialized symbol 'reg'.

First one my brining in check to already existing if condition and
second one by adding a default switch case to avoid any access to reg.

Reported-by: Dan Carpenter <dan.carpenter@oracle.com>
Signed-off-by: Srinivas Kandagatla <srinivas.kandagatla@linaro.org>
Link: https://lore.kernel.org/r/20210621134502.19537-2-srinivas.kandagatla@linaro.org
Signed-off-by: Mark Brown <broonie@kernel.org>