ASoc: wcd: mbhc: Change keycode mapping and linein_th

1. Change the key code mapping of buttons as below
 according to Android L spec.

Button0 0-70 ohm - hook key
Button1 110-180 ohm - voice assist
Button2 210-290 ohm - volume up
Button3 360-680 ohm - volume down

2. Report SW_LINEOUT_INSERT
if headset speaker impedance is larger than 5 Kohm

CRs-Fixed: 863767
Change-Id: Icb12e00a2839e11ef6b947b158c58e9e0f1404b2
Signed-off-by: Walter Yang <yandongy@codeaurora.org>