amd-xgbe: Allow for a greater number of Rx queues

Remove the call to netif_get_num_default_rss_queues() and replace it
with num_online_cpus() to allow for the possibility of using all of
the hardware DMA channels available.

Signed-off-by: Tom Lendacky <thomas.lendacky@amd.com>
Signed-off-by: David S. Miller <davem@davemloft.net>