mem/cxl-type3: Add sn option to provide serial number for PCI ecap

mem/cxl-type3: Add sn option to provide serial number for PCI ecap

The Device Serial Number Extended Capability PCI r6.0 sec 7.9.3
provides a standard way to provide a device serial number as
an IEEE defined 64-bit extended unique identifier EUI-64.

CXL 2.0 section 8.1.12.2 Memory Device PCIe Capabilities and
Extended Capabilities requires this to be used to uniquely
identify CXL memory devices.

Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>
Message-Id: <20220923161835.9805-1-Jonathan.Cameron@huawei.com>
Reviewed-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
Reviewed-by: Ben Widawsky <bwidawsk@kernel.org>