drm/i915: Silence valleyview_set_rps()

Even with the rps debug messages signficantly recuced  by
 commit 67956867
 Author: Ville Syrjälä <ville.syrjala@linux.intel.com>
 Date:   Tue Sep 2 15:12:17 2014 +0300

    drm/i915: Don't spam dmesg with rps messages on vlv/chv

we still get an inordinate amount of spam from this. Just kill the debug
print. If someone wants to observe it they can just use the tracepoint.

Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Reviewed-by: Deepak <S&lt;deepak.s@linux.intel.com>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>