drm/i915: Make intel_dp_set_m_n take crtc_state

Another user of crtc->config gone. The functions it calls also
needed crtc->config, so convert those as well.

Signed-off-by: Maarten Lankhorst <maarten.lankhorst@linux.intel.com>
[mlankhorst: Still pass m_n struct to intel_pch_transcoder_set_m_n (Ville)]
Reviewed-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20181011100457.8776-3-maarten.lankhorst@linux.intel.com