bootloaders: add bootloaders-next manifest
For the SDK 10.0 release, we have been requested to maintain 2 versions of bootloaders:
- U-Boot 2023.04: the stable release, can be fetched with bootloaders.xml
- U-Boot 2024.04: the next release, can be fetched with bootloaders-next.xml
Add a new manifest for U-Boot 2024.04 so that users can try it out and experiment with the new bootmeth_android bootflow.
Signed-off-by: Mattijs Korpershoek mkorpershoek@baylibre.com