drm/i915: Eliminate intel_dp.regs.dp_tp_{ctl,status}

drm/i915: Eliminate intel_dp.regs.dp_tp_{ctl,status}

Now that we've plumbed the crtc state all the way down we can
eliminate the DP_TP_{CTL,STATUS} register offsets from intel_dp,
and instead we derive them directly from the crtc state.

And thus we can get rid of the nasty hack in intel_ddi_get_config()
which mutates intel_dp during the readout.

Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20200929233449.32323-12-ville.syrjala@linux.intel.com
Reviewed-by: Imre Deak <imre.deak@intel.com>