net: ena: fix update of interrupt moderation register

Current implementation always updates the interrupt register with
the smoothed_interval of the rx_ring. However this should be
done only in case of adaptive interrupt moderation. If non-adaptive
interrupt moderation is used, the non-adaptive interrupt moderation
interval should be used. This commit fixes that.

Signed-off-by: Arthur Kiyanovski <akiyano@amazon.com>
Signed-off-by: David S. Miller <davem@davemloft.net>