drm/panfrost: Add arm,mali-valhall-jm compatible

The most important Valhall-specific quirks have been handled, so add the
Valhall compatible and probe.

v2: Use arm,mali-valhall-jm compatible.

Reviewed-by: Steven Price <steven.price@arm.com>
Signed-off-by: Alyssa Rosenzweig <alyssa.rosenzweig@collabora.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20220525145754.25866-10-alyssa.rosenzweig@collabora.com