ci: Update tf-m version in FIH test

To a version which uses the new bootutil cmake, allowing the bootutil
files to be moved/renamed without breaking the FIH test.

Signed-off-by: Raef Coles <raef.coles@arm.com>
diff --git a/ci/fih_test_docker/Dockerfile b/ci/fih_test_docker/Dockerfile
index f4b743a..0dbd059 100644
--- a/ci/fih_test_docker/Dockerfile
+++ b/ci/fih_test_docker/Dockerfile
@@ -39,7 +39,10 @@
 # Clone TF-M and dependencies
 RUN mkdir -p /root/work/tfm &&\
     cd /root/work/tfm  &&\
-    git clone https://git.trustedfirmware.org/TF-M/trusted-firmware-m.git -b TF-Mv1.2-RC1 &&\
+    git clone https://git.trustedfirmware.org/TF-M/trusted-firmware-m.git &&\
+    cd trusted-firmware-m &&\
+    git checkout 7ad5c5f23f4619add4aa6c88f4b25fc6fd84ec6e &&\
+    cd .. &&\
     mkdir mcuboot
 
 # Copy the test execution script to the image