ext4 crypto: require CONFIG_CRYPTO_CTR if ext4 encryption is enabled

On arm64 this is apparently needed for CTS mode to function correctly.
Otherwise attempts to use CTS return ENOENT.

Change-Id: I3f597f5f88e806dbeed75a7123c3d6bb7e608350
Signed-off-by: Theodore Ts'o <tytso@mit.edu>
Signed-off-by: "Theodore Ts'o" <tytso@google.com>