drm/rockchip: rk3066_hdmi: Switch encoder hooks to atomic

The rk3066_hdmi encoder still uses the non atomic variants
of enable and disable. Convert to their atomic equivalents.
In atomic mode there is no need to save the adjusted mode,
so remove the mode_set function.

Signed-off-by: Johan Jonker <jbx6244@gmail.com>
Signed-off-by: Heiko Stuebner <heiko@sntech.de>
Link: https://patchwork.freedesktop.org/patch/msgid/034c3446-d619-f4c3-3aaa-ab51dc19d07f@gmail.com