drm/i915/kbl: Remove preliminary_hw_support protection from KBL.

We now have KBL machines running in our CI systems and with no
blocking issues that could cause a full hangs or blank screens.

Signed-off-by: Rodrigo Vivi <rodrigo.vivi@intel.com>
Link: http://patchwork.freedesktop.org/patch/msgid/1459349881-951-1-git-send-email-rodrigo.vivi@intel.com


Acked-by: Daniel Vetter <daniel.vetter@ffwll.ch>