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

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

Change-Id: I2e3b8eed08316fcd7534c680961f597149977eff