drm/i915: Add bigjoiner state dump

Add a big of bigjoiner information to the state dump.

Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Signed-off-by: Manasi Navare <manasi.d.navare@intel.com>
Reviewed-by: Manasi Navare <manasi.d.navare@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20201117194718.11462-15-manasi.d.navare@intel.com