Merge "hikey/hikey960: support to specify the prebuilt kernel dir out of aosp tree" am: 4dca84db28 am: 54813f6269 am: c0345b8683

Original change: https://android-review.googlesource.com/c/device/linaro/hikey/+/1508145

Change-Id: Ibcaf0940d568293e9966a3659d2f28c3027263a3