qoriq_dw_pci: Fix typo in link status checking code

On some DesignWare PCIe controllers accessing config registers of slots
whose link is down triggers a SError. Because of that we need to check the
link status before any acceses config space.
Due to a typo link was always reported up.
This fixes a SError that occured during boot on LS1028A-RDB.

Obtained from: Semihalf
Reviewed by: wma
Differential revision: https://reviews.freebsd.org/D31509

(cherry picked from commit df9c0e88e1e30cb5d1c81c4c2f295f7d153ed02b)