fs: prepend statmount.mnt_opts string with security_sb_mnt_opts()

Currently these mount options aren't accessible via statmount().

The read handler for /proc/#/mountinfo calls security_sb_show_options()
to emit the security options after emitting superblock flag options, but
before calling sb->s_op->show_options.

Have statmount_mnt_opts() call security_sb_show_options() before
calling ->show_options.

Signed-off-by: Jeff Layton <jlayton@kernel.org>
Link: https://lore.kernel.org/r/20241115-statmount-v2-2-cd29aeff9cbb@kernel.org


Signed-off-by: Christian Brauner <brauner@kernel.org>