mlx5e: don't assume anything on the irq affinity mappings of the device

mlx5e currently assumes that irq affinity is really spread first
irq vectors across device home node cpus, with the new generic affinity
mappings this is no longer the case, hence mlxe should not rely on
this anymore.

Signed-off-by: Sagi Grimberg <sagi@grimberg.me>
Signed-off-by: Doug Ledford <dledford@redhat.com>