drm/ci: mediatek: add tests for mediatek display driver

For mediatek mt8183, the display driver is mediatek, while the
gpu driver is panfrost. Currently, in drm-ci for mt8183, only
the gpu driver is tested. Refactor the existing mediatek jobs
and add support in drm-ci to test both display and gpu driver
for mt8183 and update xfails.

Since the correct driver name is passed from the job to test gpu
and display driver, remove the check to set IGT_FORCE_DRIVER
based on driver name for mediatek jobs.

Update the MAINTAINERS file to include xfails for panfrost driver.

Signed-off-by: Vignesh Raman <vignesh.raman@collabora.com>