drm/i915: s/intel_crtc_bw/intel_dbuf_bw/

Rename the intel_crtc_bw struct to intel_dbuf_bw to better
reflect what it does.

Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20250326162544.3642-3-ville.syrjala@linux.intel.com


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