tf-a-main, tf-a-lts2.8-main: Explicitly define MBEDTLS_URL

Mainline vs LTS use different mbedTLS versions, and make this fact explicit
by specifying exact version to use for *both* jobs.

The version for LTS is based on https://linaro.atlassian.net/browse/TFC-451.

Signed-off-by: Paul Sokolovsky <paul.sokolovsky@linaro.org>
Change-Id: I359949dc2d05bd3a66f00b41b8d5ba0ca4d10d29
diff --git a/tf-a-main.yaml b/tf-a-main.yaml
index 67ace42..de150f4 100644
--- a/tf-a-main.yaml
+++ b/tf-a-main.yaml
@@ -43,6 +43,9 @@
             name: CI_REFSPEC
             default: '+refs/heads/master:refs/remotes/origin/master'
         - string:
+            name: MBEDTLS_URL
+            default: 'https://github.com/Mbed-TLS/mbedtls/archive/mbedtls-3.4.0.tar.gz'
+        - string:
             name: SHARE_FOLDER
             default: '/srv/shared/${JOB_NAME}/${BUILD_NUMBER}'
             description: 'Folder containing shared repositories for downstream pipeline jobs'