PCI: pci-bridge-emul: Properly mark reserved PCIe bits in PCI config space

PCI: pci-bridge-emul: Properly mark reserved PCIe bits in PCI config space

BugLink: https://bugs.launchpad.net/bugs/1959376
commit 7b067ac63a5730d2fae18399fed7e45f23d36912 upstream.

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: 23a5fba4d941 ("PCI: Introduce PCI bridge emulated config space common logic")
Signed-off-by: Pali Rohár <pali@kernel.org>
Signed-off-by: Lorenzo Pieralisi <lorenzo.pieralisi@arm.com>
Cc: stable@vger.kernel.org
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Paolo Pisati <paolo.pisati@canonical.com>