sfc: default config to 1 channel/core in local NUMA node only

Handling channels from CPUs in different NUMA node can penalize
performance, so better configure only one channel per core in the same
NUMA node than the NIC, and not per each core in the system.

Fallback to all other online cores if there are not online CPUs in local
NUMA node.

Signed-off-by: Íñigo Huguet <ihuguet@redhat.com>
Acked-by: Martin Habets <habetsm.xilinx@gmail.com>
Signed-off-by: Jakub Kicinski <kuba@kernel.org>