drm/i915: Really calculate the cursor ddb based on the highest enabled wm level

I added the loop but neglected to actually pass the level to the
function. So we were just looping 8 times calculating the exact
same thing every time.

Fixes: df331de3 ("drm/i915: Allocate enough DDB for the cursor")
Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20190321175128.32178-1-ville.syrjala@linux.intel.comReviewed-by: Rodrigo Vivi <rodrigo.vivi@intel.com>

drivers/gpu/drm/i915/intel_pm.c

@@ -3953,7 +3953,7 @@ skl_cursor_allocation(const struct intel_crtc_state *crtc_state,
 	WARN_ON(ret);
 
 	for (level = 0; level <= max_level; level++) {
-		skl_compute_plane_wm(crtc_state, 7, &wp, &wm, &wm);
+		skl_compute_plane_wm(crtc_state, level, &wp, &wm, &wm);
 		if (wm.min_ddb_alloc == U16_MAX)
 			break;