bnx2x: Revise IOV vlan/mac validation

There are several places in IOV related flows where PF needs to determine
whether a VF slowpath elements have already been configured (i.e., this
affect its ability to configure/remove classifications for the VF).

This patch changes the conditions for the validation and performs a cleaner
validation (e.g., by replacing several validations with a single one).

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>