Some bits in PCI config space are reserved when device is PCIe. Properly
define behavior of PCI registers for PCIe emulated bridge and ensure that
it would not be possible change these reserved bits.

Link: https://lore.kernel.org/r/20211124155944.1290-3-pali@kernel.org
Fixes: 23a5fba4 ("PCI: Introduce PCI bridge emulated config space common logic")
Signed-off-by: NPali Rohár <pali@kernel.org>
Signed-off-by: NLorenzo Pieralisi <lorenzo.pieralisi@arm.com>
Cc: stable@vger.kernel.org