west.yml: MCUboot synchronization from upstream

Update Zephyr fork of MCUboot to revision:
  4eba8087fa606db801455f14d185255bc8c49467

Brings following Zephyr relevant fixes:

  - 4eba8087 boot: zephyr: boards config of the stm32h573 disco kit
  - 2dd7c655 boot: zephyr: boards config of the stm32h7rs target
    boards
  - cde66e17 boot: zephyr: defines FLASH device for external NOR
  - 6a178d29 bootutil: Use flash base address for direct hash

Signed-off-by: Jamie McCrae <jamie.mccrae@nordicsemi.no>