ASoc: q6afe: add support to get port direction

This patch adds support to q6afe_is_rx_port() to get direction
of DSP BE dai port, this is useful for setting dailink
directions correctly.

Fixes: c25e295c (ASoC: qcom: Add support to parse common audio device nodes")
Reported-by: John Stultz <john.stultz@linaro.org>
Signed-off-by: Srinivas Kandagatla <srinivas.kandagatla@linaro.org>
Signed-off-by: John Stultz <john.stultz@linaro.org>