hikey: README: Update documentation to use boot.img instead of boot_fat.uefi.img am: c5ec19591f
am: 94a6345d20

* commit '94a6345d20cb5f703d4b56e44f218f3838699942':
  hikey: README: Update documentation to use boot.img instead of boot_fat.uefi.img

Change-Id: Id81f2fce0e7e8589cd130b8a52ce86faf6b4bc0a