drm/amdgpu: Improve MES responsiveness during oversubscription

When MES is oversubscribed it may not frequently check for new
command submissions from driver if the scheduling load is high.
Response latency as high as 5 seconds has been observed.

Enable a flag which adds a check for new commands between
scheduling quantums.

Signed-off-by: Jay Cornwall <jay.cornwall@amd.com>
Cc: Alexandru Tudor <alexandru.tudor@amd.com>
Reviewed-by: Harish Kasiviswanathan <Harish.Kasiviswanathan@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>