drm/i915/gt: Make timeslicing an explicit engine property

drm/i915/gt: Make timeslicing an explicit engine property

[ Upstream commit fe5a708267911d55cce42910d93e303924b088fd ]

In order to allow userspace to rely on timeslicing to reorder their
batches, we must support preemption of those user batches. Declare
timeslicing as an explicit property that is a combination of having the
kernel support and HW support.

Suggested-by: Tvrtko Ursulin <tvrtko.ursulin@intel.com>
Fixes: 8ee36e048c98 ("drm/i915/execlists: Minimalistic timeslicing")
Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Cc: Tvrtko Ursulin <tvrtko.ursulin@intel.com>
Reviewed-by: Tvrtko Ursulin <tvrtko.ursulin@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20200501122249.12417-1-chris@chris-wilson.co.uk
(cherry picked from commit a211da9c771bf97395a3ced83a3aa383372b13a7)
Signed-off-by: Rodrigo Vivi <rodrigo.vivi@intel.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>