Merge "db845c.mk: set DB845C_KERNEL_DIR to use environment when specified" am: fe771fcdfb am: 2ae5a2a2e6

Original change: https://android-review.googlesource.com/c/device/linaro/dragonboard/+/1462043

Change-Id: I2dccea5928646b49145d27b35c55b9d221f4f417