drm/sun4i: Add compatible strings for A80 TCONs

The A80 has 2 or 3 TCONs. The documentation and vendor kernel are very
vague about the third TCON, to the point that it might not exist.

In the documentation, the first TCON is missing channel 1, and the
second is missing channel 0. However the vendor kernel seems to be
able to use them regardless. Here we model them like the old TCONs.

An oddity is that TCON0 requires the reset control for the eDP block
to be deasserted, for any register access to stick.

This patch adds compatible strings for TCON0 and TCON1, with TCON0
requiring an extra "edp" reset control.

Reviewed-by: Rob Herring <robh@kernel.org>
Signed-off-by: Chen-Yu Tsai <wens@csie.org>
Signed-off-by: Maxime Ripard <maxime.ripard@bootlin.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20180315114136.24747-2-wens@csie.org