MIPS: Octeon: Add PCIe link status check

In the Linux kernel, the following vulnerability has been resolved:

MIPS: Octeon: Add PCIe link status check

The standard PCIe configuration read-write interface is used to

access the configuration space of the peripheral PCIe devices

of the mips processor after the PCIe link surprise down, it can

generate kernel panic caused by "Data bus error". So it is

necessary to add PCIe link status check for system protection.

When the PCIe link is down or in training, assigning a value

of 0 to the configuration address can prevent read-write behavior

to the configuration space of peripheral PCIe devices, thereby

preventing kernel panic.