use Arm's jenkins environment check function

Use the function that checks Arm's jenkins environment instead of 'echo
| grep' pipe command

Signed-off-by: Leonardo Sandoval <leonardo.sandoval@linaro.org>
Change-Id: I99060e330d3cc64569d4d3638684c6e0ad2bee73
diff --git a/model/fvp_common.sh b/model/fvp_common.sh
index 2f9cd17..ef29c3b 100644
--- a/model/fvp_common.sh
+++ b/model/fvp_common.sh
@@ -82,7 +82,7 @@
 
 EOF
 
-if echo "$JENKINS_URL" | grep -q -v "arm.com"; then
+if ! is_arm_jenkins_env; then
 	cat <<EOF >>"$model_param_file"
 -C bp.pl011_uart0.untimed_fifos=1
 -C bp.pl011_uart1.untimed_fifos=1