fvp_utils.sh: gen_fvp_yaml: Output warning if called without template

Signed-off-by: Paul Sokolovsky <paul.sokolovsky@linaro.org>
Change-Id: I182d7534329bec2c99b97739eb1f8049c00b931a
(cherry picked from commit a3c5a4c06243c1404de6ecc75e07afab754736ac)
diff --git a/fvp_utils.sh b/fvp_utils.sh
index 0c90bb7..c87f423 100644
--- a/fvp_utils.sh
+++ b/fvp_utils.sh
@@ -325,6 +325,7 @@
 
     # this function expects a template, quit if it is not present
     if [ ! -f "$yaml_template_file" ]; then
+        echo "warning: gen_fvp_yaml: template $yaml_template_file not available, skipping generating LAVA job"
 	return
     fi