[ Upstream commit e7519f99 ]

Take uld mutex to avoid race between cxgb_up() and
cxgb4_register_uld() to enable napi for the same uld
queue.
Signed-off-by: Ganesh Goudar <ganeshgr@chelsio.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>