drm/i915: Do more bw readout

Update a bunch of bw related stuff during readout:
- bw_state->dbuf_bw possible now that the wm readout
  has given us access to the plane ddb data
- cdclk_state->bw_min_cdclk

Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20250326162544.3642-7-ville.syrjala@linux.intel.com


Reviewed-by: Jani Nikula <jani.nikula@intel.com>