qed: Fix possible race for the link state value.

There's a possible race where driver can read link status in mid-transition
and see that virtual-link is up yet speed is 0. Since in this
mid-transition we're guaranteed to see a mailbox from MFW soon, we can
afford to treat this as link down.

Fixes: cc875c2e ("qed: Add link support")
Signed-off-by: Sudarsana Reddy Kalluru <Sudarsana.Kalluru@cavium.com>
Signed-off-by: Ariel Elior <ariel.elior@cavium.com>
Signed-off-by: Michal Kalderon <Michal.Kalderon@cavium.com>
Signed-off-by: David S. Miller <davem@davemloft.net>