cxgb4: fix checks for max queues to allocate

Hardware can support more than 8 queues currently limited by
netif_get_num_default_rss_queues(). So, rework and fix checks for max
number of queues to allocate. The checks should be based on how many are
actually supported by hardware, OR the number of online cpus; whichever
is lower.

Fixes: 5952dde7 ("cxgb4: set maximal number of default RSS queues")
Signed-off-by: Vishal Kulkarni <vishal@chelsio.com&gt;">
Signed-off-by: David S. Miller <davem@davemloft.net>