kernel-resin.bbclass: Add missing CONFIG_BTRFS_FS_POSIX_ACL
kernel-resin.bbclass: Add missing CONFIG_BTRFS_FS_POSIX_ACL

We use docker's btrfs storage driver and hence rely on linux btrfs filesystem support.
In this scenario, without setting the kernel CONFIG_BTRFS_FS_POSIX_ACL option, docker
complains when trying to start user containers:

failed to register layer: ApplyLayer exit status 1 stdout: stderr: operation not supported'

Signed-off-by: Florin Sarbu <3a837a37a2ac9072a088641ec330e0e5d5b86f4e@resin.io>

resin-os/meta-resin,resin-os/meta-resin,resin-os/meta-resin,resin-os/meta-resin