drm/sun4i: hdmi: Convert encoder to atomic

The sun4i_hdmi driver still uses the non-atomic variants of the encoder
hooks, so let's convert to their atomic equivalents.

Acked-by: Sui Jingfeng <sui.jingfeng@linux.dev>
Reviewed-by: Jernej Skrabec <jernej.skrabec@gmail.com>
Signed-off-by: Maxime Ripard <mripard@kernel.org>
Link: https://patchwork.freedesktop.org/patch/msgid/20240222-kms-hdmi-connector-state-v7-32-8f4af575fce2@kernel.org