f2fs: reject test_dummy_encryption when !CONFIG_FS_ENCRYPTION

There is no good reason to allow this mount option when the kernel isn't
configured with encryption support.  Since this option is only for
testing, we can just fix this; we don't really need to worry about
breaking anyone who might be counting on this option being ignored.
Signed-off-by: Eric Biggers <ebiggers@google.com>
Signed-off-by: Jaegeuk Kim <jaegeuk@kernel.org>

fs/f2fs/super.c

@@ -525,10 +525,11 @@ static int f2fs_set_test_dummy_encryption(struct super_block *sb,
 		return -EINVAL;
 	}
 	f2fs_warn(sbi, "Test dummy encryption mode enabled");
+	return 0;
 #else
-	f2fs_warn(sbi, "Test dummy encryption mount option ignored");
+	f2fs_warn(sbi, "test_dummy_encryption option not supported");
+	return -EINVAL;
 #endif
-	return 0;
 }
 
 #ifdef CONFIG_F2FS_FS_COMPRESSION