drm/i915: Pass intel_dbuf_bw to skl_*_calc_dbuf_bw() explicitly

Make skl_*_calc_dbuf_bw() a bit lower level passing in the
to be mutated dbuf_bw struct in explicitly. This will allow
more reuse later.

Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20250326162544.3642-5-ville.syrjala@linux.intel.com


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