ixgbe: Streamline MC filter setup for VFs

The driver was calling the set Rx mode function for every multicast
filter set by the VF.  When starting many VMs where each might have
multiple VLAN interfaces this would result in the function being
called hundreds or even thousands of times.  This is unnecessary
for the case of the imperfect filters used in the MTA and has been
streamlined to be more efficient.

Signed-off-by: Greg Rose <gregory.v.rose@intel.com>
Signed-off-by: Jeff Kirsher <jeffrey.t.kirsher@intel.com>
Signed-off-by: David S. Miller <davem@davemloft.net>