ASoc: wcd: mbhc: Change the key code mapping of buttons

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

CRs-Fixed: 863767
Change-Id: If4f616c913a4aeadd3b15cea81ac000d93258c09
Signed-off-by: Walter Yang <yandongy@codeaurora.org>