This function was private to the QEMU driver and was,
accordingly, called qemuDomainPCIBusFullyReserved().

However the function is really not QEMU-specific at
all, so it makes sense to move it closer to the
virDomainPCIAddressBus struct it operates on.
Signed-off-by: NAndrea Bolognani <abologna@redhat.com>
Reviewed-by: NLaine Stump <laine@laine.org>