ixgbe, ixgbevf: Add new mbox API xcast mode

The limitation of the number of multicast address for VF is not enough
for the large scale server with SR-IOV feature. IPv6 requires the multicast
MAC address for each IP address to handle the Neighbor Solicitation
message. We couldn't assign over 30 IPv6 addresses to a single VF.

This patch introduces the new mailbox API, IXGBE_VF_UPDATE_XCAST_MODE,
to update multicast mode of VF. This adds 3 modes;
  - NONE     only L2 exact match addresses or Flow Director enabled
  - MULTI    BAM and ROMPE set
  - ALLMULTI BAM, ROMPE and MPE set

If a guest VF user wants over 30 MAC multicast addresses, set IFF_ALLMULTI
to request PF to update xcast mode to enable VF multicast promiscuous mode.

On the other hand, enabling VF multicast promiscuous mode may affect
security and performance in the network of the NIC. Only trusted VF can
enable multicast promiscuous mode. The behavior of untrusted VF is the
same as previous version.

Signed-off-by: Hiroshi Shimamoto <h-shimamoto@ct.jp.nec.com>
Tested-by: Krishneil Singh <Krishneil.k.singh@intel.com>
Signed-off-by: Jeff Kirsher <jeffrey.t.kirsher@intel.com>