drm/i915: Pass the crtc state explicitly to intel_pipe_update_start/end()

Pass the appropriate new crtc state explicitly to
intel_pipe_update_start/end() instead of of mucking around with
crtc->state.

v2: The mmio flip stuff is gone

Reviewed-by: Maarten Lankhorst <maarten.lankhorst@linux.intel.com> #v1
Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20170823152226.22938-2-ville.syrjala@linux.intel.com