ext4: Do not override ext2 or ext3 if built they are built as modules

The CONFIG_EXT4_USE_FOR_EXT23 option must not try to take over the
ext2 or ext3 file systems if the those file system drivers are
configured to be built as mdoules.

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

fs/ext4/Kconfig

@@ -28,7 +28,7 @@ config EXT4_FS
 
 config EXT4_USE_FOR_EXT23
 	bool "Use ext4 for ext2/ext3 file systems"
-	depends on !EXT3_FS || !EXT2_FS
+	depends on EXT3_FS=n || EXT2_FS=n
 	default y
 	help
 	  Allow the ext4 file system driver code to be used for ext2 or