ASoC: msm8939: changes to connect external speaker to HPH

Add widgets to provide a switch that connects external speaker
PA to HPH left or right. Enable the external PA GPIO in the
dapm power up sequence when this switch connects external PA
to HPH left or right.

Change-Id: Ic3b430628a4cc15c8a5ac35d9f5335f6b97a2423
Signed-off-by: Meng Wang <mwang@codeaurora.org>