PCI: pciehp: ignore undefined bit in link status register

Bit 10 in Link Status register used to be defined as Training Error in
the PCI Express 1.0a specification. But it was removed by Training Error
ECN and is no longer defined. So pciehp must ignore the value read from
it.

Signed-off-by: Kenji Kaneshige <kaneshige.kenji@jp.fujitsu.com>
Signed-off-by: Jesse Barnes <jbarnes@virtuousgeek.org>