ASoC: msm8x10-wcd: Enable impedance detection

Add support to compute impedance of the headphone left and right
impedance.  Once impedance is known the codec parameters can be adjusted
to increase the efficiency of audio output to headphones. Impedance
detection is disabled by default and can be enabled at runtime through
module parameter.

Change-Id: I281859f8486e5787d4699c207a9da80e5c235960
Signed-off-by: Bhalchandra Gajare <gajare@codeaurora.org>