auxdisplay/ptn3460: Add driver for NXP PTN3460

auxdisplay/ptn3460: Add driver for NXP PTN3460

Add a new driver to handle the NXP PTN3460 DP/LVDS bridge chip. The
driver currently gets its platform data from device tree. In its current
state, it only supports power up/down using PD_N & RST_N pins.

BUG=chrome-os-partner:10829
BUG=chrome-os-partner:11158
BUG=chrome-os-partner:12046
TEST=Tested on snow, screen came up on power-on and resume

Change-Id: Ic9c7884edfe514ae5ab646b172c4c47352d46276
Signed-off-by: Sean Paul <seanpaul@chromium.org>
Reviewed-on: https://gerrit.chromium.org/gerrit/29239
Reviewed-by: Olof Johansson <olofj@chromium.org>