drm/i915: Ditch SUPPORTS_INTEGRATED_HDMI|DP and use IS_G4X instead

Since that's really what we want to test for. Note remove the gen5
case doesn't change anything: In intel_setup_outputs ilk is handled
already in the HAS_PCH_SPLIT case, and the register save/restore code
touches registers which simply doesn't exist anymore at all.

v2: Drop UMS parts.

v3: Update commit message to reflect that the reg save/restore code is
gone (Ville).

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