ixgbe(4): Filter out spurious link up indication

Extend SFP+ cage crosstalk fix by re-checking link state after 5ms delay
to filter out spurious link up indication by transceiver with no fiber
cable connected.

Signed-off-by: Krzysztof Galazka <krzysztof.galazka@intel.com>
Signed-off-by: Eric Joyner <erj@FreeBSD.org>

Reviewed by: erj@
Tested by: Gowtham Kumar Ks <gowtham.kumar.ks@intel.com>
MFC after: 3 days
Sponsored by: Intel Corporation
Differential Revision: https://reviews.freebsd.org/D38395