src/signature: support intermediate certificates in cms_get_cert_chain()
src/signature: support intermediate certificates in cms_get_cert_chain()

This patch enables extracting extra certificates contained in
CMS_ContentInfo and forwards it to the X509_STORE_CTX used for
verification.

Signed-off-by: Enrico Joerns <a2e5f936c390f36494e46e71bcfbe365bb1e8c49@pengutronix.de>

jluebbe/rauc,ejoerns/rauc,ejoerns/rauc,jluebbe/rauc,rauc/rauc,rauc/rauc,ejoerns/rauc,rauc/rauc,jluebbe/rauc