build-kernel-deb: enable CONFIG_CEPH_FSCACHE if possible

CephFS FS-Cache support went into 3.12 merge window, we need to start
building it.

Signed-off-by: Ilya Dryomov <ilya.dryomov@inktank.com>
build-kernel-deb: enable CONFIG_CEPH_FS_POSIX_ACL if possible

CephFS ACLs went into 3.14 merge window, start building that code.

Signed-off-by: Ilya Dryomov <ilya.dryomov@inktank.com>