msmcobalt: file_context: Add file context for non-hlos mount points

The non-hlos mount points(/firmware and /bt_firmware) are now built
as a part of the image rather than being created on the fly. Adding
the labels for both of them here. Also added a rule to allow init to
mount the non-hlos partitions on the same.

Change-Id: Idb2bf7cb3894421ef78354cb965e7fbb77627172