PCI: keystone: Add link up check in ks_child_pcie_ops.map_bus()

commit bd1e414ea86c1dfead731b8d5eb8b187a735ffa4 from
git://git.ti.com/ti-linux-kernel/ti-linux-kernel.git



K2G forwardS the error triggered by a link-down state (e.g.,
no connected endpoint device) on the system bus for PCI configuration
transactions; these errors are reported as an SError at system level,
which is fatal and hangs the system. So fix it similar to how
it was done in designware core driver
commit 15b23906 ("PCI: dwc: Add link up check in
dw_child_pcie_ops.map_bus()").

Fixes: 10a797c6 ("PCI: dwc: keystone: Use pci_ops for config space accessors")
Signed-off-by: Kishon Vijay Abraham I <kishon@ti.com>
Link: https://lore.kernel.org/all/20210324121901.1856-3-kishon@ti.com/


Signed-off-by: Achal Verma <a-verma1@ti.com>
Signed-off-by: Xulin Sun <xulin.sun@windriver.com>