net: fec: add enet-avb IP support

i.MX6SX Enet-AVB support 3 tx queues, 3 rx queues.
For tx queues: ring 0 -> best effort
	       ring 1 -> Class A
	       ring 2 -> Class B
For rx queues:
	       ring 0 -> best effort
	       ring 1 -> receive VLAN packet with classification match
	       ring 2 -> receive VLAN packet with classification match

Add enet-avb IP multiqueue support for the driver.

Signed-off-by: Fugang Duan <B38611@freescale.com>
Signed-off-by: Frank Li <Frank.Li@freescale.com>
Signed-off-by: David S. Miller <davem@davemloft.net>