pcie/spdm: PCIe CMA implementation

The Data Object Exchange implementation of Component Measurement
and Authentication (CMA). This patch is basically based on libspdm:
https://github.com/DMTF/spdm_emu



spdm_emu is an emulator composed of an SPDM requester and an SPDM
responder. The requester and responder communicate with each other via
a TCP socket. The spdm_emu requester is merged to this patch as a DOE
capability in hw/mem/cxl_type3.c. "-spdm=<port_number>" is provided to turn
on/off the CMA capability. Once the option is turned on (e.g. -spdm=2323) the
CXL device can communicate with Openspdm's responder to get the data
object of SPDM/secured SPDM.

Upstream spdm_emu_responder is currently hardcoded to only use port
2323.  If this approach goes ahead, a --port option will be proposed
for that tool.

Signed-off-by: hchkuo <hchkuo@avery-design.com.tw>
Signed-off-by: Chris Browy <cbrowy@avery-design.com>
Co-developed-by: Jonathan Cameron <Jonathan.cameron@huawei.com>
Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>