net: axienet: start napi before enabling Rx/Tx

softirq may get lost if an Rx interrupt comes before we call
napi_enable. Move napi_enable in front of axienet_setoptions(), which
turns on the device, to address the issue.

Link: https://lists.gnu.org/archive/html/qemu-devel/2024-07/msg06160.html
Fixes: cc37610c

 ("net: axienet: implement NAPI and GRO receive")
Signed-off-by: Andy Chiu <andy.chiu@sifive.com>
Reviewed-by: Eric Dumazet <edumazet@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>