west.yml: MCUboot synchronization from upstream

Update Zephyr fork of MCUboot to revision:
  eb942067989569f9cf319b087d0bb16b16effd86

Brings following Zephyr relevant fixes:
  - eb942067 Allow bootstrapping for multiple images
  - d59ae346 boot_serial: Support sha256, sha384 and sha512
  - bcffc62c boot: bootutil: boot_record: Fix issue with saving
    image data
  - 099f4284 boot: zephyr: Add fallback for overhead calculation
    when auto fails
  - ab014436 boards: mcxn947_qspi: fix mcuboot partition allocation
  - bd7423d1 boot: zephyr: Add warning on default key file usage
  - a03c95f6 doc: remove repetition
  - 040fc42a boot/zephyr: Load image to RAM on single loader
  - 84c68ace boot/zephyr: Add
    CONFIG_SINGLE_APPLICATION_SLOT_RAM_LOAD
  - 77d911f4 boot/bootutil: Add
    MCUBOOT_SINGLE_APPLICATION_SLOT_RAM_LOAD mode
  - 0c721da7 boot/bootutil: Split RAM load code to its own file

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