CHROMIUM: auxdisplay/ps8620: Add driver for Parade PS8622 bridge

CHROMIUM: auxdisplay/ps8620: Add driver for Parade PS8622 bridge

Add a new driver to handle the Parade PS8622 eDP/LVDS bridge chip.
The driver sets properly the SLP_N and RST_N pins and configure the
bridge through I2C.

Signed-off-by: Vincent Palatin <vpalatin@chromium.org>
BUG=chrome-os-partner:14491
TEST=Tested on Spring, see the screen coming up on boot.

Change-Id: I3fd15f9780abe45b1cc93f9234db7d79c65ac5a3
Reviewed-on: https://gerrit.chromium.org/gerrit/36231
Reviewed-by: Sean Paul <seanpaul@chromium.org>
Commit-Ready: Vincent Palatin <vpalatin@chromium.org>
Tested-by: Vincent Palatin <vpalatin@chromium.org>