dragonboards: fix boot and vendor_boot partition sizes am: b8380ce018 am: eff1beab3f am: 3d61d7d98d am: dbd0677d8c

Original change: https://android-review.googlesource.com/c/device/linaro/dragonboard/+/2781187

Change-Id: Ibe3eec076f61b1f6ecaa97de7ecde9e4621dba72
Signed-off-by: Automerger Merge Worker <android-build-automerger-merge-worker@system.gserviceaccount.com>