drm/i915: Fix FB WM for HSW

Due to a misplaced memset(), we never actually enabled the FBC WM on HSW.
Move the memset() to happen a bit earlier, so that it won't clobber
results->enable_fbc_wm.
Signed-off-by: NVille Syrjälä <ville.syrjala@linux.intel.com>
Reviewed-by: NPaulo Zanoni <paulo.r.zanoni@intel.com>
Signed-off-by: NDaniel Vetter <daniel.vetter@ffwll.ch>

drivers/gpu/drm/i915/intel_pm.c

@@ -2681,6 +2681,8 @@ static void hsw_compute_wm_results(struct drm_device *dev,
 			break;
 	max_level = level - 1;
 
+	memset(results, 0, sizeof(*results));
+
 	/* The spec says it is preferred to disable FBC WMs instead of disabling
 	 * a WM level. */
 	results->enable_fbc_wm = true;
@@ -2691,7 +2693,6 @@ static void hsw_compute_wm_results(struct drm_device *dev,
 		}
 	}
 
-	memset(results, 0, sizeof(*results));
 	for (wm_lp = 1; wm_lp <= 3; wm_lp++) {
 		const struct intel_wm_level *r;