hikey960: Add /metadata support (reusing cache partition)

With dynamic partitions we need /metadata mounted to properly
make 'adb remount' work.

So this makes use of the unused cache partition to mount it as
metadata (along with the needed build env values).

With this patch 'adb remount' works.

Signed-off-by: John Stultz <john.stultz@linaro.org>
Change-Id: I33da79ec15b453dbdc3b8a3180863abeb67d4cb6
3 files changed