Set Cert: incorrect key usage check for AliasCert Model

[rw8896]

libspdm/library/spdm_crypt_lib/libspdm_crypt_cert.c

Lines 1193 to 1197 in b327ead

	if ((LIBSPDM_CRYPTO_X509_KU_DIGITAL_SIGNATURE & value) == 0) {
	status = false;
	goto cleanup;
	}
	}

When set_cert is true and cert model is SPDM_CERTIFICATE_INFO_CERT_MODEL_ALIAS_CERT, the leaf cert is device CA cert which doesn't need to have the digitalSignature usage. Probably could check keyCertSign instead.

[steven-bellock]

Probably could check keyCertSign instead.

In the SPDM specification Key Usage is only mandatory for leaf certificates. For now libspdm can just skip the check.