drm/i915: BDW needs D_COMP writes through MCHBAR
drm/i915: BDW needs D_COMP writes through MCHBAR

That's what the spec said! And HSW needs it through pcode (you can
only read it through MCHBAR), so create hsw_write_dcomp to abstract
the weirdness.

Signed-off-by: Paulo Zanoni <cc0e04a2103c45cd195651d976f79813d0f66bdf@intel.com>
Reviewed-by: Imre Deak <fbd5edba1988036c8923f0cca0cce6ac4811db29@intel.com>
Signed-off-by: Daniel Vetter <c1b6782c4af8f0673da8923a0702a1832e5940f4@ffwll.ch>

KristFoundation/Programs,KristFoundation/Programs,KristFoundation/Programs,KristFoundation/Programs,KristFoundation/Programs,KristFoundation/Programs