drm/i915: Kill INTEL_SUBPLATFORM_AML

drm/i915: Kill INTEL_SUBPLATFORM_AML

All AML parts are either KBL ULX or CFL ULX so there is no point
in keeping INTEL_SUBPLATFORM_AML around. As these are the only
CFL ULX parts (normal CFL didn't have Y SKUs) so we'll just
replace IS_AML_ULX with IS_CFL_ULX (it was already paired with
IS_KBL_ULX which accounts for the other half of the AML parts).

Cc: Tvrtko Ursulin <tvrtko.ursulin@intel.com>
Cc: José Roberto de Souza <jose.souza@intel.com>
Cc: Rodrigo Vivi <rodrigo.vivi@intel.com>
Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20190605162946.19223-2-ville.syrjala@linux.intel.com
Reviewed-by: Rodrigo Vivi <rodrigo.vivi@intel.com>