drm/i915: Avoid triggering unwanted cdclk changes due to dbuf bandwidth changes

drm/i915: Avoid triggering unwanted cdclk changes due to dbuf bandwidth changes

Currently intel_bw_calc_min_cdclk() always adds the bw_state
to the atomic state. Not only does it result in potentially
redundant work later, it's also currently causing unwanted cdclk
changes during driver load.

Check if the dbuf bw is actually changing before we decide to
pull in the bw state.

Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20250326162544.3642-6-ville.syrjala@linux.intel.com
Reviewed-by: Jani Nikula <jani.nikula@intel.com>