feat(rmmd): el3 token sign during attestation

Add required SMCs by RMM to push attestation signing requests to EL3
and get responses. EL3 may then choose to push these requests to a HES
as suitable for a platform. This patch also supports the new
RMM_EL3_FEATURES interface, that RMM can use to query for support for
HES based signing. The new interface exposes a feature register with
different bits defining different discoverable features. This new
interface is available starting the 0.4 version of the RMM-EL3
interface, causing the version to bump up. This patch also adds a
platform port for FVP that implements the platform hooks required to
enable the new SMCs, but it does not push to a HES and instead copies a
zeroed buffer in EL3.

Change-Id: I69c110252835122a9533e71bdcce10b5f2a686b2
Signed-off-by: Raghu Krishnamurthy <raghupathyk@nvidia.com>
diff --git a/Makefile b/Makefile
index 179e07a..cc9060a 100644
--- a/Makefile
+++ b/Makefile
@@ -1177,6 +1177,7 @@
 	HW_ASSISTED_COHERENCY \
 	MEASURED_BOOT \
 	DICE_PROTECTION_ENVIRONMENT \
+	RMMD_ENABLE_EL3_TOKEN_SIGN \
 	DRTM_SUPPORT \
 	NS_TIMER_SWITCH \
 	OVERRIDE_LIBC \
@@ -1331,6 +1332,7 @@
 	ENABLE_PMF \
 	ENABLE_PSCI_STAT \
 	ENABLE_RME \
+	RMMD_ENABLE_EL3_TOKEN_SIGN \
 	ENABLE_RUNTIME_INSTRUMENTATION \
 	ENABLE_SME_FOR_NS \
 	ENABLE_SME2_FOR_NS \