LoongArch: Add PCI controller support

mainline inclusion
from mainline-v6.0-rc1
commit 57fc7323
category: feature
bugzilla: https://gitee.com/openeuler/kernel/issues/I5OHOB


CVE: NA

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Loongson64 based systems are PC-like systems which use PCI/PCIe as its
I/O bus, This patch adds the PCI host controller support for LoongArch.

Reviewed-by: WANG Xuerui <git@xen0n.name>
Signed-off-by: Jianmin Lv <lvjianmin@loongson.cn>
Signed-off-by: Huacai Chen <chenhuacai@loongson.cn>