net: mvneta: Configure XPS support

With this patch each CPU is associated with its own set of TX queues.

It also setup the XPS with an initial configuration which set the
affinity matching the hardware configuration.

Suggested-by: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Gregory CLEMENT <gregory.clement@free-electrons.com>
Signed-off-by: David S. Miller <davem@davemloft.net>