PCI: loongson: Use generic 8/16/32-bit config ops on LS2K/LS7A

LS2K/LS7A support 8/16/32-bits PCI config access operations via CFG1, so
we can disable CFG0 for them and safely use pci_generic_config_read()/
pci_generic_config_write() instead of pci_generic_config_read32()/pci_
generic_config_write32().

Link: https://lore.kernel.org/r/20220714124216.1489304-3-chenhuacai@loongson.cn


Signed-off-by: Huacai Chen <chenhuacai@loongson.cn>
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>
Acked-by: Bjorn Helgaas <bhelgaas@google.com>