RFC: drm/lcdc: add TI LCD Controller DRM driver (v2)

A simple DRM/KMS driver for the TI LCD Controller found in various
smaller TI parts (AM33xx, OMAPL138, etc).  This driver uses the
CMA helpers.  Currently only the TFP410 DVI encoder is supported
(tested with beaglebone + DVI cape).  There are also various LCD
displays, for which support can be added (as I get hw to test on),
and an external i2c HDMI encoder found on some boards.

The display controller supports a single CRTC.  And the encoder+
connector are split out into sub-devices.  Depending on which LCD
or external encoder is actually present, the appropriate output
module(s) will be loaded.

v1: original
v2: fix fb refcnting and few other cleanups

Signed-off-by: Rob Clark <robdclark@gmail.com>
RFC: drm/lcdc: add support for LCD panels

Add an output panel driver for LCD panels.  Tested with LCD3 cape on
beaglebone.

TODO: need some way to control the appropriate backlight device
TODO: probably want to make the DT bindings more generic for panel-info

Signed-off-by: Rob Clark <robdclark@gmail.com>
devicetree entries for lcdc..
HACK: fix clk names
HACK: fix lcdc device name

hack until I can figure out how to make hwmod clk names match
devicetree..  otherwise device name ends up "4830e000.fb" and
clk_get() fails
drm: i2c encoder helper wrappers
WIP: drm/i2c: nxp-tda998x

Driver for the NXP TDA998X i2c hdmi encoder slaves.
WIP: drm/lcdc: add encoder slave..
dt updates