hikey960: Switch default flash-all to use the UEFI bootloader. am: 7f18a5391f am: d6c0e0409d am: 2aed91067f am: fecf1d099d

Original change: https://android-review.googlesource.com/c/device/linaro/hikey/+/1665239

Change-Id: Ie034c122f640628282dd8dccc62955bf56296602