drm/i915/gvt: Kick scheduler when new workload queued

The current schedule policy rely on a 1ms timer to execute workload. This
can introduce maximum 1ms unnecessary latency. This is especially bad for
small media workloads.

And I don't think we need this timer for QoS, but the change is not simply
remove the code. So I made a new API intel_gvt_kick_schedule() for future
change.

Signed-off-by: Changbin Du <changbin.du@intel.com>
Signed-off-by: Zhenyu Wang <zhenyuw@linux.intel.com>