drm/mediatek: Add DRM Driver for Mediatek SoC MT8173.

This patch adds an initial DRM driver for the Mediatek MT8173 DISP
subsystem. It currently supports two fixed output streams from the
OVL0/OVL1 sources to the DSI0/DPI0 sinks, respectively.

Signed-off-by: CK Hu <ck.hu@mediatek.com>
Signed-off-by: YT Shen <yt.shen@mediatek.com>
Signed-off-by: Daniel Kurtz <djkurtz@chromium.org>
Signed-off-by: Bibby Hsieh <bibby.hsieh@mediatek.com>
Signed-off-by: Mao Huang <littlecvr@chromium.org>
Signed-off-by: Philipp Zabel <p.zabel@pengutronix.de>

drivers/gpu/drm/Kconfig

@@ -288,3 +288,5 @@ source "drivers/gpu/drm/etnaviv/Kconfig"
 source "drivers/gpu/drm/arc/Kconfig"
 
 source "drivers/gpu/drm/hisilicon/Kconfig"
+
+source "drivers/gpu/drm/mediatek/Kconfig"