dev-arm: SCMI Implementation

JIRA: https://gem5.atlassian.net/browse/GEM5-768

Change-Id: I8a60418c1edc79c3f403905618af3bc7989f114e
Signed-off-by: Giacomo Travaglini <giacomo.travaglini@arm.com>
Reviewed-on: https://gem5-review.googlesource.com/c/public/gem5/+/34379
Tested-by: kokoro <noreply+kokoro@google.com>
Reviewed-by: Andreas Sandberg <andreas.sandberg@arm.com>
Maintainer: Andreas Sandberg <andreas.sandberg@arm.com>

src/dev/arm/css/SConscript

@@ -39,8 +39,12 @@ Import('*')
 
 if env['TARGET_ISA'] == 'arm':
     SimObject('MHU.py')
+    SimObject('Scmi.py')
     SimObject('Scp.py')
 
     Source('mhu.cc')
+    Source('scmi_platform.cc')
+    Source('scmi_protocols.cc')
 
     DebugFlag('MHU')
+    DebugFlag('SCMI')