drm/panel: Add driver for Seiko 43WVF1G panel

drm/panel: Add driver for Seiko 43WVF1G panel

Add driver for Seiko Instruments Inc. 4.3" WVGA (800 x RGB x 480)
TFT with Touch-Panel.

Datasheet available at:
http://www.glyn.de/data/glyn/media/doc/43wvf1g-0.pdf

Seiko 43WVF1G panel has two power supplies: avdd and dvdd and they
require a specific power on/down sequence.
For this reason the simple panel driver cannot be used to drive this
panel, so create a new one heavily based on simple panel.

Based on initial patch submission from Breno Lima.

Signed-off-by: Marco Franchi <marco.franchi@nxp.com>
Signed-off-by: Thierry Reding <treding@nvidia.com>
Link: https://patchwork.freedesktop.org/patch/msgid/1500567179-6967-1-git-send-email-marco.franchi@nxp.com