The lock for protecting the reference table is declared as an
RWLOCK, although it is only used in write mode, never in read
mode.

We redefine it to become a spinlock.
Signed-off-by: Jon Maloy <jon.maloy@ericsson.com>
Reviewed-by: Ying Xue <ying.xue@windriver.com>
Reviewed-by: Erik Hugne <erik.hugne@ericsson.com>
Signed-off-by: David S. Miller <davem@davemloft.net>