Update RSS platform

Build arm/rss/tc instead of arm/rss, due to RSS platform split

Change-Id: Idaef39fcc33416325459439a9f3df598f84dd0cb
Signed-off-by: Raef Coles <raef.coles@arm.com>
diff --git a/build_helper/build_helper_configs.py b/build_helper/build_helper_configs.py
index 50f1409..3df0e7a 100755
--- a/build_helper/build_helper_configs.py
+++ b/build_helper/build_helper_configs.py
@@ -608,7 +608,7 @@
                 }
 
 config_rss = {"seed_params": {
-                "tfm_platform":     ["arm/rss"],
+                "tfm_platform":     ["arm/rss/tc"],
                 "compiler":         ["GCC_10_3"],
                 "isolation_level":  ["1", "2"],
                 "test_regression":  [True, False],