drm/ingenic: Add support for JZ4780 and HDMI output

Add support for the LCD controller present on JZ4780 SoCs.
This SoC uses 8-byte descriptors which extend the current
4-byte descriptors used for other Ingenic SoCs.

Tested on MIPS Creator CI20 board.

Signed-off-by: Paul Boddie <paul@boddie.org.uk>
Signed-off-by: Ezequiel Garcia <ezequiel@collabora.com>
Signed-off-by: H. Nikolaus Schaller <hns@goldelico.com>
Signed-off-by: Paul Cercueil <paul@crapouillou.net>
Link: https://patchwork.freedesktop.org/patch/msgid/caf9e56b64b0717563e03172b30fa03736e92e15.1638470392.git.hns@goldelico.com