igb/igbvf: Add VF MAC filter request capabilities

Add functionality for the VF to request up to 3 additional MAC filters.
This is done using existing E1000_VF_SET_MAC_ADDR message, but with
additional message info - E1000_VF_MAC_FILTER_CLR to clear all unicast
MAC filters previously set for this VF and E1000_VF_MAC_FILTER_ADD to
add MAC filter.

Additional filters can be added only in case if administrator did not
set VF MAC explicitly and allowed to change default MAC to the VF.

Due to the limited number of RAR entries reserve at least 3 MAC filters
for the PF.

If SRIOV is supported by the NIC after this change RAR entries starting
from 1 to (RAR MAX ENTRIES - NUM SRIOV VFS) will be used for PF and VF
MAC filters.

Signed-off-by: Yury Kylulin <yury.kylulin@intel.com>
Tested-by: Aaron Brown <aaron.f.brown@intel.com>
Signed-off-by: Jeff Kirsher <jeffrey.t.kirsher@intel.com>