ixgbevf: avoid adding twice the permanent mac address

ixgbevf: avoid adding twice the permanent mac address

During the initialization of a VF device, the rte_eth_dev_start() function
indirectly invokes the PMD "mac_addr_add" function with the permanent MAC
address assigned to the device.
In the case of 82599 VFs, this operation leads to exhausting the very
limited set of PF resources used to store VF MAC addresses.

To address this issue, do nothing in the function ixgbevf_add_mac_addr()
if the added MAC address is equal to the permanent MAC address of the VF.

Signed-off-by: Ivan Boule <ivan.boule@6wind.com>
Acked-by: Thomas Monjalon <thomas.monjalon@6wind.com>