soundwire: qcom: add debugfs entry for soundwire register dump

For debug purposes add an entry in debugfs to dump Qualcomm
SoundWire Controller registers.

Signed-off-by: Srinivas Kandagatla <srinivas.kandagatla@linaro.org>
Link: https://lore.kernel.org/r/20210907105636.3171-1-srinivas.kandagatla@linaro.org


Signed-off-by: Vinod Koul <vkoul@kernel.org>