arm/arm64: Add PCI Express 1.1 support

PCI Express comes with an extended addressing scheme, which directly
translated into a bigger device configuration space (256->4096 bytes)
and bigger PCI configuration space (16->256 MB), as well as mandatory
capabilities (power management [1] and PCI Express capability [2]).

However, our virtio PCI implementation implements version 0.9 of the
protocol and it still uses transitional PCI device ID's, so we have
opted to omit the mandatory PCI Express capabilities. For VFIO, the power
management and PCI Express capability are left for a subsequent patch.

[1] PCI Express Base Specification Revision 1.1, section 7.6
[2] PCI Express Base Specification Revision 1.1, section 7.8

Signed-off-by: Alexandru Elisei <alexandru.elisei@arm.com>