Older kernels don't support encryption with casefolding. This adds
the sysfs entry encrypted_casefold to show support for those combined
features. Support for this feature was originally added by
commit 7ad08a58bf67 ("f2fs: Handle casefolding with Encryption")
Fixes: 7ad08a58bf67 ("f2fs: Handle casefolding with Encryption")
Cc: stable@xxxxxxxxxxxxxxx # v5.11+
Signed-off-by: Daniel Rosenberg <drosen@xxxxxxxxxx>