cppcheck: Use the mirror Mcuboot from tf.org

Signed-off-by: Karl Zhang <karl.zhang@arm.com>
Change-Id: I8b4ee034ee93ca37fc487d71d2f76360fa001969
diff --git a/tf-m-cppcheck.yaml b/tf-m-cppcheck.yaml
index af6ee2a..0065a3d 100644
--- a/tf-m-cppcheck.yaml
+++ b/tf-m-cppcheck.yaml
@@ -56,7 +56,7 @@
           default: 'v1.6.0'
       - string:
           name: 'MCUBOOT_URL'
-          default: 'https://github.com/JuulLabs-OSS/mcuboot.git'
+          default: 'https://git.trustedfirmware.org/mirror/mcuboot.git'
       - string:
           name: 'TFM_TESTS_URL'
           default: 'https://git.trustedfirmware.org/TF-M/tf-m-tests.git'