Build : Update tf-m-tests repo version

Update tf-m-tests repo version to f6b208d.

Change-Id: If025844d4266c7c69f4bba809921ed94a87d5524
Signed-off-by: Shawn Shan <Shawn.Shan@arm.com>
diff --git a/lib/ext/tf-m-tests/repo_config_default.cmake b/lib/ext/tf-m-tests/repo_config_default.cmake
index 084f899..83df1f2 100644
--- a/lib/ext/tf-m-tests/repo_config_default.cmake
+++ b/lib/ext/tf-m-tests/repo_config_default.cmake
@@ -8,5 +8,5 @@
 # Default configs of tf-m-tests repo
 
 set(TFM_TEST_REPO_PATH                  "DOWNLOAD"  CACHE PATH      "Path to TFM-TEST repo (or DOWNLOAD to fetch automatically")
-set(TFM_TEST_REPO_VERSION               "65efae1"   CACHE STRING    "The version of tf-m-tests to use")
+set(TFM_TEST_REPO_VERSION               "f6b208d"   CACHE STRING    "The version of tf-m-tests to use")
 set(CMSIS_5_PATH                        "DOWNLOAD"  CACHE PATH      "Path to CMSIS_5 (or DOWNLOAD to fetch automatically")