net: ena: Change default print level for netif_ prints

The netif_* functions are used by the driver to log events into the
kernel ring (dmesg) similar to the netdev_* ones. Unlike the latter,
the netif_* function family allow the user to choose what events get
logged using ethtool:
	sudo ethtool -s [interface] msglvl [msg_type] on

By default the events which get logged are slow-path related and aren't
printed often (e.g. interface up related prints). This patch removes the
NETIF_MSG_TX_DONE type (called every TX completion polling) from the
defaults and adds NETIF_MSG_IFDOWN instead as it makes more sensible
defaults.

This patch also transforms ena_down() print from netif_info into
netif_dbg (same as the analogue print in ena_up()) as it suits it
better.

Signed-off-by: Shay Agroskin <shayagr@amazon.com>
Signed-off-by: David Arinzon <darinzon@amazon.com>
Signed-off-by: Paolo Abeni <pabeni@redhat.com>