db845c|rb5: Switch to android-6.6 as the default kernel version am: e969c450d2

Original change: https://android-review.googlesource.com/c/device/linaro/dragonboard/+/3018836

Change-Id: I7632a7793639ff5902bccd401f84437304e79d0e
Signed-off-by: Automerger Merge Worker <android-build-automerger-merge-worker@system.gserviceaccount.com>