drm/mediatek: mtk_dpi: Explicitly manage TVD clock in power on/off

[ Upstream commit 473c33f5ce651365468503c76f33158aaa1c7dd2 ]

In preparation for adding support for MT8195's HDMI reserved
DPI, add calls to clk_prepare_enable() / clk_disable_unprepare()
for the TVD clock: in this particular case, the aforementioned
clock is not (and cannot be) parented to neither pixel or engine
clocks hence it won't get enabled automatically by the clock
framework.

Please note that on all of the currently supported MediaTek
platforms, the TVD clock is always a parent of either pixel or
engine clocks, and this means that the common clock framework
is already enabling this clock before the children.
On such platforms, this commit will only increase the refcount
of the TVD clock without any functional change.

Reviewed-by: CK Hu <ck.hu@mediatek.com>
Signed-off-by: AngeloGioacchino Del Regno <angelogioacchino.delregno@collabora.com>
Link: https://patchwork.kernel.org/project/dri-devel/patch/20250217154836.108895-10-angelogioacchino.delregno@collabora.com/


Signed-off-by: Chun-Kuang Hu <chunkuang.hu@kernel.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>