drm/i915: Pass crtc_state to update_scanline_offset

No need to look at crtc->config when we have crtc_state in the caller.

Signed-off-by: Maarten Lankhorst <maarten.lankhorst@linux.intel.com>
Reviewed-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20181011100457.8776-6-maarten.lankhorst@linux.intel.com