Support authentication of uefi priv. variables

To authenticate private uefi variables a fingerprint has to be
calculated based on the common name of the signing certificate's
Subject field and the tbsCertificate of the top-level issuer
certificate.
These variables have a public key certificate attached so the
verify_pkcs7_signature_handler is also reorganized to be able
to verify its own signature with its internal public key.
This commit implements the changes needed for the described
functionality.

Signed-off-by: Gabor Toth <gabor.toth2@arm.com>
Change-Id: Ida22977f3ef1a730ea95834ca5c9f9e4ed78d927
diff --git a/deployments/crypto/crypto.cmake b/deployments/crypto/crypto.cmake
index 098861c..963dde5 100644
--- a/deployments/crypto/crypto.cmake
+++ b/deployments/crypto/crypto.cmake
@@ -8,6 +8,7 @@
 add_components(TARGET "crypto"
 	BASE_DIR ${TS_ROOT}
 	COMPONENTS
+		"components/common/mbedtls"
 		"components/common/tlv"
 		"components/rpc/common/interface"
 		"components/rpc/common/endpoint"