drm/panfrost: Add "clean only safe" feature bit

Add the HW_FEATURE_CLEAN_ONLY_SAFE bit based on kbase. When I actually
tried to port the logic from kbase, trivial jobs raised Data Invalid
Faults, so this may depend on other coherency details. It's still useful
to have the bit to record the feature bit when adding new models.

Reviewed-by: Steven Price <steven.price@arm.com>
Signed-off-by: Alyssa Rosenzweig <alyssa.rosenzweig@collabora.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20220525145754.25866-7-alyssa.rosenzweig@collabora.com