xen: workaround missing device_type property in pci/pcie nodes

xen: workaround missing device_type property in pci/pcie nodes

PCI buses differ from default buses in a few important ways, so it is
important to detect them properly. Normally, PCI buses are expected to
have the following property:

    device_type = "pci"

In reality, it is not always the case. To handle PCI bus nodes that
don't have the device_type property, also consider the node name: if the
node name is "pcie" or "pci" then consider the bus as a PCI bus.

This commit is based on the Linux kernel commit
d1ac0002dd29 "of: address: Work around missing device_type property in
pcie nodes".

This fixes Xen boot on RPi4. Some RPi4 kernels have the following node
on their device trees:

&pcie0 {
	pci@1,0 {
		#address-cells = <3>;
		#size-cells = <2>;
		ranges;

		reg = <0 0 0 0 0>;

		usb@1,0 {
			reg = <0x10000 0 0 0 0>;
			resets = <&reset RASPBERRYPI_FIRMWARE_RESET_ID_USB>;
		};
	};
};

The pci@1,0 node is a PCI bus. If we parse the node and its children as
a default bus, the reg property under usb@1,0 would have to be
interpreted as an address range mappable by the CPU, which is not the
case and would break.

Link: https://lore.kernel.org/xen-devel/YBmQQ3Tzu++AadKx@mattapan.m5p.com/
[fix style on commit]
Signed-off-by: Stefano Stabellini <stefano.stabellini@xilinx.com>
Tested-by: Elliott Mitchell <ehem+xen@m5p.com>
Tested-by: Jukka Kaartinen <jukka.kaartinen@unikie.com>
Reviewed-by: Bertrand Marquis <bertrand.marquis@arm.com>
Acked-by: Julien Grall <jgrall@amazon.com>