drm/mediatek: dp: Add phy_mtk_dp module as pre-dependency

drm/mediatek: dp: Add phy_mtk_dp module as pre-dependency

The mtk_dp driver registers a phy device which is handled by the
phy_mtk_dp driver and assumes that the phy probe will complete
synchronously, proceeding to make use of functionality exposed by that
driver right away. This assumption however is false when the phy driver
is built as a module, causing the mtk_dp driver to fail probe in this
case.

Add the phy_mtk_dp module as a pre-dependency to the mtk_dp module to
ensure the phy module has been loaded before the dp, so that the phy
probe happens synchrounously and the mtk_dp driver can probe
successfully even with the phy driver built as a module.

Suggested-by: AngeloGioacchino Del Regno <angelogioacchino.delregno@collabora.com>
Fixes: f70ac097a2cf ("drm/mediatek: Add MT8195 Embedded DisplayPort driver")
Signed-off-by: Nícolas F. R. A. Prado <nfraprado@collabora.com>
Reviewed-by: AngeloGioacchino Del Regno <angelogioacchino.delregno@collabora.com>
Reviewed-by: Guillaume Ranquet <granquet@baylibre.com>
Link: https://patchwork.kernel.org/project/dri-devel/patch/20231121142938.460846-1-nfraprado@collabora.com/
Signed-off-by: Chun-Kuang Hu <chunkuang.hu@kernel.org>