Simple function to search a PCIBus to find a port by
it's port number.

CXL interleave decoding uses the port number as a target
so it is necessary to locate the port when doing interleave
decoding.

Signed-off-by: Jonathan Cameron <jonathan.cameron@huawei.com>
Reviewed-by: Alex Bennée <alex.bennee@linaro.org>
Message-Id: <20220429144110.25167-31-Jonathan.Cameron@huawei.com>
Reviewed-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>