drm/i915: Restore ILK-M RPS support

drm/i915: Restore ILK-M RPS support

Restore RPS for ILK-M. We lost it when an extra HAS_RPS()
check appeared in intel_rps_enable().

Unfortunaltey this just makes the performance worse on my
ILK because intel_ips insists on limiting the GPU freq to
the minimum. If we don't do the RPS init then intel_ips will
not limit the frequency for whatever reason. Either it can't
get at some required information and thus makes wrong decisions,
or we mess up some weights/etc. and cause it to make the wrong
decisions when RPS init has been done, or the entire thing is
just wrong. Would require a bunch of reverse engineering to
figure out what's going on.

Cc: stable@vger.kernel.org
Cc: Chris Wilson <chris@chris-wilson.co.uk>
Fixes: 9c878557b1eb ("drm/i915/gt: Use the RPM config register to determine clk frequencies")
Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20201021131443.25616-1-ville.syrjala@linux.intel.com
Reviewed-by: Chris Wilson <chris@chris-wilson.co.uk>