drm/i915: Continuation of future readiness series

Removing the check for HAS_PCH_SPLIT, it looks redundant here. Anyways all the
platforms are checked separately.

v2: Reordering as per the gen (Ville)

Signed-off-by: Sonika Jindal <sonika.jindal@intel.com>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>