drm/i915/bxt: Don't uninit/init display core twice during system suspend/resume

Atm, we run the BSpec display core uninit/init sequences twice during
system suspend/resume. While this shouldn't cause any problem, it's
redundant, so get rid of the duplicate call.

Signed-off-by: Imre Deak <imre.deak@intel.com>
Reviewed-by: Bob Paauwe <bob.j.paauwe@intel.com>
Link: http://patchwork.freedesktop.org/patch/msgid/1461173277-16090-3-git-send-email-imre.deak@intel.com