drm/i915/display/adlp: Adjust MBUS DBOX BW and B credits

Alderlake-P has different MBUS DBOX BW and B credits than other
platforms, so here setting it properly.

BSpec: 49213
BSpec: 50343
Cc: Matt Roper <matthew.d.roper@intel.com>
Cc: Stanislav Lisovskiy <stanislav.lisovskiy@intel.com>
Cc: Jani Nikula <jani.nikula@intel.com>
Cc: Ville Syrjälä <ville.syrjala@linux.intel.com>
Reviewed-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Signed-off-by: Caz Yokoyama <caz.yokoyama@intel.com>
Signed-off-by: José Roberto de Souza <jose.souza@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20220330155724.255226-2-jose.souza@intel.com