ALSA: add headphone over current switches

Some CODECs monitor current drawn by headphone power amplifer.
If current consumed goes over pre-defined threshold, CODEC would
communicate to host processor. Then, CODEC driver would propagate
the event so user-space application can react accordingly.
Add support to propagate over current events for both
left headphone and right headphone through ALSA jack framework.

Change-Id: Ieef36f070a4478a5a80ec4c8b0cc81464abd75ad
Signed-off-by: Patrick Lai <plai@codeaurora.org>