ext4 crypto: do not select from EXT4_FS_ENCRYPTION

This patch adds a tristate EXT4_ENCRYPTION to do the selections
for EXT4_FS_ENCRYPTION because selecting from a bool causes all
the selected options to be built-in, even if EXT4 itself is a
module.

Signed-off-by: Herbert Xu <[e-mail]>
Signed-off-by: Theodore Ts'o <[e-mail]>

fs/ext4/Kconfig

···
 	  If you are not using a security module that requires using
 	  extended attributes for file security labels, say N.
 
-config EXT4_FS_ENCRYPTION
-	bool "Ext4 Encryption"
+config EXT4_ENCRYPTION
+	tristate "Ext4 Encryption"
 	depends on EXT4_FS
 	select CRYPTO_AES
 	select CRYPTO_CBC
···
 	  feature is similar to ecryptfs, but it is more memory
 	  efficient since it avoids caching the encrypted and
 	  decrypted pages in the page cache.
+
+config EXT4_FS_ENCRYPTION
+	bool
+	default y
+	depends on EXT4_ENCRYPTION
 
 config EXT4_DEBUG
 	bool "EXT4 debugging support"