ext4: Only advertise encrypted_casefold when encryption and unicode are enabled

Encrypted casefolding is only supported when both encryption and
casefolding are both enabled in the config.

Fixes: 471fbbea

 ("ext4: handle casefolding with encryption")
Cc: stable@vger.kernel.org # 5.13+
Signed-off-by: Daniel Rosenberg <drosen@google.com>
Link: https://lore.kernel.org/r/20210603094849.314342-1-drosen@google.com


Signed-off-by: Theodore Ts'o <tytso@mit.edu>