drm/i915: Make the rps new_delay comparison more readable

Eliminate the weird inverted logic from the rps new_delay comparison.

Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Reviewed-by: Jesse Barnes <jbarnes@virtuousgeek.org>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>