drm/i915: Read power well status before other registers for drpc info

Trying to read the status of the power wells right after taking forcewake
for the other register reads makes little sense. Most of the time the
power wells will still be up due to the recent forcewake. Instead do the
power well status read first, and only then read the register needing
forcewake. This way the reported power well status can actually reflect
what's going on in the system.

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