firewire: fix small memory leak at module removal

Signed-off-by: Stefan Richter <stefanr@s5r6.in-berlin.de>
diff --git a/drivers/firewire/fw-device.c b/drivers/firewire/fw-device.c
index 6b9be42..31b6c74 100644
--- a/drivers/firewire/fw-device.c
+++ b/drivers/firewire/fw-device.c
@@ -617,7 +617,7 @@
  */
 DECLARE_RWSEM(fw_device_rwsem);
 
-static DEFINE_IDR(fw_device_idr);
+DEFINE_IDR(fw_device_idr);
 int fw_cdev_major;
 
 struct fw_device *fw_device_get_by_devt(dev_t devt)