ASoC: wcd_cpe_core: add support to select CPE AFE port

Currently only one CPE AFE output port is supported. Add
an API to get CPE AFE port ID from codec driver. Use that
port ID for LAB buffering.

Change-Id: I74fdeb1800a64ed775608967e4d315f28d48e9ef
Signed-off-by: Vidyakumar Athota <vathota@codeaurora.org>