This patch adds an MMIO interface for each virtio-pci device, so that
they can be accessed without having to use an ioport. For each device, a
new memory BAR is added which corresponds to an area of MMIO space with
a shim trap handler. This handler simply translates the access into an
ioport access via kvm__emulate_io. Since guests can generate accesses
via either the ioport or MMIO regions, an ioeventfd is registered for
both.

Signed-off-by: Will Deacon <will.deacon@arm.com>
Signed-off-by: Pekka Enberg <penberg@kernel.org>