mogami: various wl12xx updates

Cleanup gpio definitions
Fix wifi power GPIO configuration, taken from 4.1.B.1.13 stock kernel
Undervolt to 1,8v since wl12xx supports this voltage

Signed-off-by: Michael Bestas <mikeioannina@gmail.com>

Change-Id: I52fe78a41cbeb42e47facebd39bd1da212aae83a