vfio: virqfd_lock can be static

Signed-off-by: NFengguang Wu <fengguang.wu@intel.com>
Reviewed-by: NEric Auger <eric.auger@linaro.org>
Signed-off-by: NAlex Williamson <alex.williamson@redhat.com>

drivers/vfio/virqfd.c

@@ -16,7 +16,7 @@
 #include <linux/slab.h>
 
 static struct workqueue_struct *vfio_irqfd_cleanup_wq;
-DEFINE_SPINLOCK(virqfd_lock);
+static DEFINE_SPINLOCK(virqfd_lock);
 
 int __init vfio_virqfd_init(void)
 {