fscrypt: remove filesystem specific build config option

In order to have a common code base for fscrypt "post read" processing
for all filesystems which support encryption, this commit removes
filesystem specific build config option (e.g. CONFIG_EXT4_FS_ENCRYPTION)
and replaces it with a build option (i.e. CONFIG_FS_ENCRYPTION) whose
value affects all the filesystems making use of fscrypt.

Reviewed-by: Eric Biggers <ebiggers@google.com>
Signed-off-by: Chandan Rajendra <chandan@linux.vnet.ibm.com>
Signed-off-by: Eric Biggers <ebiggers@google.com>
diff --git a/fs/ubifs/Kconfig b/fs/ubifs/Kconfig
index bc1e082..9da2f13 100644
--- a/fs/ubifs/Kconfig
+++ b/fs/ubifs/Kconfig
@@ -8,6 +8,7 @@
 	select CRYPTO_LZO if UBIFS_FS_LZO
 	select CRYPTO_DEFLATE if UBIFS_FS_ZLIB
 	select CRYPTO_HASH_INFO
+	select UBIFS_FS_XATTR if FS_ENCRYPTION
 	depends on MTD_UBI
 	help
 	  UBIFS is a file system for flash devices which works on top of UBI.
@@ -60,17 +61,6 @@
 
 	  If unsure, say Y.
 
-config UBIFS_FS_ENCRYPTION
-	bool "UBIFS Encryption"
-	depends on UBIFS_FS_XATTR && BLOCK
-	select FS_ENCRYPTION
-	default n
-	help
-	  Enable encryption of UBIFS files and directories. This
-	  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 UBIFS_FS_SECURITY
 	bool "UBIFS Security Labels"
 	depends on UBIFS_FS_XATTR