drm/i915: Avoid memory leak with more than 16 workarounds on a list

I forgot to free the old list when growing past 16 entries.

Luckily, as much as I checked, none of the current platforms has more than
16 workarounds on a single list.

Signed-off-by: Tvrtko Ursulin <tvrtko.ursulin@intel.com>
Fixes: 452420d22d ("drm/i915: Fuse per-context workaround handling with the common framework")
Reported-by: Chris Wilson <chris@chris-wilson.co.uk>
Reviewed-by: Chris Wilson <chris@chris-wilson.co.uk>
Link: https://patchwork.freedesktop.org/patch/msgid/20201113132510.2298483-1-tvrtko.ursulin@linux.intel.com

drivers/gpu/drm/i915/gt/intel_workarounds.c

@@ -131,8 +131,10 @@ static void _wa_add(struct i915_wa_list *wal, const struct i915_wa *wa)
 			return;
 		}
 
-		if (wal->list)
+		if (wal->list) {
 			memcpy(list, wal->list, sizeof(*wa) * wal->count);
+			kfree(wal->list);
+		}
 
 		wal->list = list;
 	}