CHANGELOG: Notes about distro changes in CI

Also state the RISC-V baseline now it's been set, as it's the reason why
RISC-V Bullseye got dropped.

Signed-off-by: Andrew Cooper <andrew.cooper3@citrix.com>
Acked-by: Oleksii Kurochko <oleksii.kurochko@gmail.com>
Reviewed-by: Denis Mukhin <dmukhin@ford.com>
Acked-by: Stefano Stabellini <sstabellini@kernel.org>
---
CC: Anthony PERARD <anthony.perard@vates.tech>
CC: Michal Orzel <michal.orzel@amd.com>
CC: Jan Beulich <jbeulich@suse.com>
CC: Julien Grall <julien@xen.org>
CC: Roger Pau Monné <roger.pau@citrix.com>
CC: Stefano Stabellini <sstabellini@kernel.org>
CC: Oleksii Kurochko <oleksii.kurochko@gmail.com>

v2:
 * New

CHANGELOG.md

@@ -10,6 +10,9 @@ The format is based on [Keep a Changelog](https://keepachangelog.com/en/1.0.0/)
  - The minimum toolchain requirements have increased for some architectures:
    - For x86, GCC 5.1 and Binutils 2.25, or Clang/LLVM 11
    - For ARM32 and ARM64, GCC 5.1 and Binutils 2.25
+   - For RISC-V, GCC 12.2 and Binutils 2.39
+ - Debian Trixie added to CI.  Debian Bullseye retired from CI for RISC-V due
+   to the baseline change.
  - Linux based device model stubdomains are now fully supported.
 
  - On x86: