drm/i915/skl: make sure LCPLL is disabled when uniniting CDCLK

Suppressing LCPLL disabling was added to avoid interfering with the DMC
firmware. It is not needed any more since we uninit CDCLK now with the
DMC deactivated (DC states disabled). We also must disable it during system
suspend as part of the Bspec "Display uninit sequence".

Signed-off-by: Imre Deak <imre.deak@intel.com>
Reviewed-by: Patrik Jakobsson <patrik.jakobsson@linux.intel.com>
Link: http://patchwork.freedesktop.org/patch/msgid/1446657859-9598-10-git-send-email-imre.deak@intel.com