net: update undefined ->ndo_change_mtu() comment

Update ->ndo_change_mtu() callback comment to remove text
about returning error in case of undefined callback. This
change makes the comment match the existing code behavior.

Signed-off-by: Magnus Damm <damm+renesas@opensource.se>
Signed-off-by: David S. Miller <davem@davemloft.net>
1 file changed