ext4 ACLs and security labels

Commit "ext4: Remove CONFIG_EXT4_FS_XATTR" removed the configuration
dependencies for ext4 xattrs from the ext4 ACLs and security labels
configuration options, but did not replace them with a dependency on
ext4 itself.  Add back the dependency on ext4 so the options only show
up if ext4 is enabled.

Signed-off-by: Valerie Aurora <val@vaaconsulting.com>
Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>
Reviewed-by: Tao Ma <boyu.mt@taobao.com>
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