bnx2x: Fix compilation when CONFIG_BNX2X_SRIOV is not set

Commit 370d4a26

 "bnx2x: Create workqueue for IOV related tasks" breaks bnx2x
compilation when CONFIG_BNX2X_SRIOV is not set - "multiple definition of
`bnx2x_schedule_iov_task'".

Reported-by: kbuild test robot <fengguang.wu@intel.com>
Signed-off-by: Yuval Mintz <Yuval.Mintz@qlogic.com>
Acked-by: Eric Dumazet <edumazet@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>