drm/mediatek: Use mailbox rx_callback instead of cmdq_task_cb

drm/mediatek: Use mailbox rx_callback instead of cmdq_task_cb

BugLink: https://bugs.launchpad.net/bugs/1987451
[ Upstream commit 1ee07a683b7e4e6ad9ad4f77fce4751741bc8ceb ]

rx_callback is a standard mailbox callback mechanism and could cover the
function of proprietary cmdq_task_cb, so use the standard one instead of
the proprietary one.

Signed-off-by: Chun-Kuang Hu <chunkuang.hu@kernel.org>
Signed-off-by: jason-jh.lin <jason-jh.lin@mediatek.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>
Signed-off-by: Kamal Mostafa <kamal@canonical.com>
Signed-off-by: Stefan Bader <stefan.bader@canonical.com>