bionic-amd64-tf-m-build: Use $DOCKER_SUFFIX when naming docker image

To separate sanity-check vs production images.

Signed-off-by: Paul Sokolovsky <paul.sokolovsky@linaro.org>
Change-Id: Iec0b9b5cb56244e2345a056d1239a8bbbc563fe0
diff --git a/bionic-amd64-tf-m-build/build.sh b/bionic-amd64-tf-m-build/build.sh
index d2bf20c..8e267a2 100755
--- a/bionic-amd64-tf-m-build/build.sh
+++ b/bionic-amd64-tf-m-build/build.sh
@@ -17,6 +17,6 @@
 
 cp -a ../setup-sshd .
 
-image=trustedfirmware/ci-${ARCHITECTURE}-${PROJECT}-ubuntu:${DISTRIBUTION}
+image=trustedfirmware/ci-${ARCHITECTURE}-${PROJECT}-ubuntu:${DISTRIBUTION}${DOCKER_SUFFIX}
 docker build --pull --tag=$image .
 echo $image > .docker-tag