drm/i915: Nuke PIPE_CONFIG_QUIRK_BIGJOINER_SLAVE

Now that the bigjoiner state readout/computation has been
made to do the right thing nuke the related state checker
quirk.

Reviewed-by: Manasi Navare <manasi.d.navare@intel.com>
Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20211022103304.24164-10-ville.syrjala@linux.intel.com