ci: Add ci_release_bootloaders.xml

This will be used by the release job in order to build bootloaders from
git.ti.com only.

We publish the commits on our gitlab.
After a new release is published, we can fetch this commit and send
it over to the TI forge.

Signed-off-by: Mattijs Korpershoek <mkorpershoek@baylibre.com>

ci_release_bootloaders.xml

+<?xml version="1.0" encoding="UTF-8"?>
+<manifest>
+    <remote  name="baylibre" fetch="https://gitlab.baylibre.com/baylibre/ti/android/aosp" />
+    <default revision="ci/release/d-android15-release" remote="baylibre" />
+
+    <project path="vendor/ti/am62x" name="vendor/ti/am62x.git" />
+</manifest>