octeon: ubnt-edgerouter: Disable PCIe

octeon: ubnt-edgerouter: Disable PCIe

Some devices lock up on PCIe initialization:

[   64.309697] PCIe: Port 0 in endpoint mode, skipping.
[   64.320496] PCIe: Initializing port 1
[   64.325257] PCIe: BIST FAILED for port 1 (0xffffffffffffffff)
(system hangs here)

Given the ER contains no PCIe peripherals, has no way to attach any
and the stock kernel doesn't have PCIe support either, just disable it.

Signed-off-by: Jakob Haufe <sur5r@sur5r.net>
Link: https://github.com/openwrt/openwrt/pull/15992
Signed-off-by: Robert Marko <robimarko@gmail.com>