mbedtls-amis.yaml: Support to build multi OS AMI

Build AMI by parameters

Signed-off-by: Arthur She <arthur.she@linaro.org>
Change-Id: If69e1c6a8e5517332c47bcf99725e4e3db32e3a6
diff --git a/mbedtls-amis.yaml b/mbedtls-amis.yaml
index e6d4f6f..a83cc4d 100644
--- a/mbedtls-amis.yaml
+++ b/mbedtls-amis.yaml
@@ -14,21 +14,18 @@
     node: build-amd64-private
     concurrent: false
     display-name: 'build AMIs for mbedtls'
-    triggers:
-        - gerrit:
-            server-name: 'review.trustedfirmware.org'
-            trigger-on:
-                - change-merged-event
-            projects:
-                - project-compare-type: 'PLAIN'
-                  project-pattern: 'next/ci/mbedtls-amis'
-                  branches:
-                    - branch-compare-type: 'PLAIN'
-                      branch-pattern: 'master'
-            silent-start: true
+    parameters:
+    - bool:
+        name: BUILD_UBUNTU_AMI
+        default: true
+        description: Build Ubuntu AMI
+    - bool:
+        name: BUILD_FREEBSD_AMI
+        default: false
+        description: Build FreeBSD AMI
     builders:
         - shell:
             !include-raw: mbedtls-amis/builders.sh
     publishers:
         - email:
-            recipients: linaro-infrastructure-errors@lists.linaro.org
+            recipients: linaro-infrastructure-errors@lists.linaro.org,arthur.she@linaro.org