drm/i915/skl: Don't check for ULT/ULX when detecting the PCH

IS_ULT() wasn't taking into account SKL so we had a warn with SPT-LP.

We don't realy need those checks here, and as we don't need to introduce
IS_SKL_ULT/ULX() at the moment, let's just drop them.

Signed-off-by: Damien Lespiau <damien.lespiau@intel.com>
Reviewed-by: Paulo Zanoni <paulo.r.zanoni@intel.com>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>