drm/i915: Clean up VLV rps code a bit

Always print both the MHz value and raw register value for rps stuff.

Also kill a somewhat pointless local 'rpe' variable and just use
dev_priv->rps.rpe_delay.

While at it clean up the caps in "GPU" and "Punit" debug messages.

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>