asoc: lahaina: add stub fe for wsa capture

When WSA is disabled, WSA related widgets is not registered and it
causes soundcard registeration fail. Add stub fe for wsa capture to
avoid soundcard registeration failure.

Change-Id: I282d843d02544aaf2f2b646aba4fca731fc6f47e
Signed-off-by: Meng Wang <mengw@codeaurora.org>