drm/i915/display: Convert intel_bw.c externally to intel_display

We already have internal interface for intel_bw.c converted to use
intel_display. Now convert the external interface as well.

Reviewed-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20250311-xe3lpd-bandwidth-update-v5-2-a95a9d90ad71@intel.com


Signed-off-by: Gustavo Sousa <gustavo.sousa@intel.com>