net: ena: Remove redundant assignment

There is no point in initializing an ndo to NULL, therefore the
assignment is redundant and can be removed.

Signed-off-by: Kamal Heib <kheib@redhat.com>
Reviewed-by: Brett Creeley <brett.creeley@amd.com>
Acked-by: Arthur Kiyanovski <akiyano@amazon.com>
Signed-off-by: David S. Miller <davem@davemloft.net>