hikey-kernel: Update prebuilt kernel to 4.1.15 (d71f3d2)
am: d29bfaf422

* commit 'd29bfaf422c09371d7cd89f8483253b7f652d79a':
  hikey-kernel: Update prebuilt kernel to 4.1.15 (d71f3d2)

Change-Id: I4b759e2d09b201e8cb74ab1be0504e9ea38d40dd