lib: spdm: improve GET_CAPABILITIES conformance

[twilfredo]

SPDM specification version 1.3 specifies that for a GET_CAPABILITIES
request, the DataTransferSize should equal MaxSPDMmsgSize, when
chunking is not used/supported.

This is not specified in the 1.2 specification currently, but a
clarification is to be added to specification 1.2.2 [1]. This patch
adds conformance to this clarification.

[1] DMTF/libspdm#2329 (comment)

[l1k]

Thank you @twilfredo, your testing and validation efforts of the in-kernel SPDM implementation are greatly appreciated.

I've amended my development branch to unconditionally set MaxSPDMmsgSize to the same value as DataTransferSize and I've added another commit at the tip of the branch which reverts MaxSPDMmsgSize to UINT_MAX again. That commit can be amended in the future with large SPDM message support.

[twilfredo]

Thank you @twilfredo, your testing and validation efforts of the in-kernel SPDM implementation are greatly appreciated.

I've amended my development branch to unconditionally set MaxSPDMmsgSize to the same value as DataTransferSize and I've added another commit at the tip of the branch which reverts MaxSPDMmsgSize to UINT_MAX again. That commit can be amended in the future with large SPDM message support.

Okay sounds good then! cheers