drm/tilcdc: add TI LCD Controller DRM driver (v4)

drm/tilcdc: add TI LCD Controller DRM driver (v4)

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
v3: get +/- vsync/hsync from timings rather than panel-info, add
    option DT max-bandwidth field so driver doesn't attempt to
    pick a display mode with too high memory bandwidth, and other
    small cleanups
v4: remove some unneeded stuff from panel-info struct, properly
    set high bits for hfp/hsw/hbp for rev 2, add DT bindings docs

Signed-off-by: Rob Clark <robdclark@gmail.com>
Reviewed-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Tested-by: Koen Kooi <koen@dominion.thruhere.net>