f2fs crypto: add f2fs encryption Kconfig

This patch adds f2fs encryption config.

This patch integrates:

"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."

Signed-off-by: Michael Halcrow <mhalcrow@google.com>
Signed-off-by: Theodore Ts'o <tytso@mit.edu>
Signed-off-by: Jaegeuk Kim <jaegeuk@kernel.org>