update the 4.14 and 4.19 prebuilt kernels am: 28cf7f4459

Original change: https://android-review.googlesource.com/c/device/ti/beagle-x15-kernel/+/1512662

Change-Id: I29dff30a2f28830cc7de0cbfec7f2b94bc94389a
tree: 4a8c4e2e611217e264b0dcae865a3758396ea81e
  1. 4.14/
  2. 4.19/