Closing/opening the adapter is not needed at all.
The new MTU settings take effect immediately.

Fixes: 97bde5c4 ("net: ethernet: aquantia: Support for NIC-specific code")
Signed-off-by: NPavel Belous <pavel.belous@aquantia.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>