qed: Prevent link getting down in case of autoneg-off.

	Newly added link modes are required to be added
	during setting link modes. If the new link mode
	is not available during qed_set_link, it may cause
	link getting down due to empty supported capability,
	being passed to MFW, after setting autoneg off/on
	with current/supported speed.

Signed-off-by: Rahul Verma <Rahul.Verma@cavium.com>
Signed-off-by: Ariel Elior <ariel.elior@cavium.com>
Signed-off-by: David S. Miller <davem@davemloft.net>