bnx2x: Correct default Tx switching behaviour

With this patch bnx2x will configure the PF to perform Tx switching on
out-going traffic as soon as SR-IOV is dynamically enabled and de-activate
it when it is disabled.
This will allow VFs to communicate with their parent PFs.

Signed-off-by: Yuval Mintz <yuvalmin@broadcom.com>
Signed-off-by: Ariel Elior <ariele@broadcom.com>
Signed-off-by: David S. Miller <davem@davemloft.net>