drm/i915: More assorted dev_priv cleanups

A small selection of macros which can only accept dev_priv from
now on and a resulting trickle of fixups.

v2: Keep original order. (Ville Syrjala)

Signed-off-by: Tvrtko Ursulin <tvrtko.ursulin@intel.com>
Cc: Ville Syrjälä <ville.syrjala@linux.intel.com>
Reviewed-by: David Weinehall <david.weinehall@linux.intel.com>