Enable setting security contexts on rootfs inodes.
rootfs (ramfs) can support setting of security contexts by userspace due to the vfs fallback behavior of calling the security module to set the in-core inode state for security.* attributes when the filesystem does not provide an xattr handler. No xattr handler required as the inodes are pinned in memory and have no backing store.
This is useful in allowing early userspace to label individual files within a rootfs while still providing a policy-defined default via genfs.
Signed-off-by: Stephen Smalley <email@example.com>