ASoC: msm8x10: Enable current source for headset detection

Headset detection can either use micbias or current source. Set the flag
in the headset detection configuration to indicate usage of current
source for headset detection rather than micbias. Using current source,
the pops and clicks during headset insertion / removal are minimized.

Change-Id: I171cff606704400b811a4e46c5a3d6cdfa8b5510
Signed-off-by: Bhalchandra Gajare <gajare@codeaurora.org>