drm/i915: Do wm readout ealier for skl+

Move the wm readout to happen earlier. This is needed because
the bw_state readout will need ddb information populated by
the wm readout.

For now limit this to skl+ as I've not really analyzed the
implications of doing this on other platforms.

Reviewed-by: Vinod Govindapillai <vinod.govindapillai@intel.com>
Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20250306163420.3961-17-ville.syrjala@linux.intel.com