f2fs: remove wrong backported codes

Kconfig and dentry RCU mode fixes.

Fixes: c1286ff ("f2fs: backport from 'for-f2fs-4.9'")
Signed-off-by: Jaegeuk Kim <jaegeuk@kernel.org>

Author: Jaegeuk Kim

fs/f2fs/Kconfig

@@ -2,7 +2,6 @@ config F2FS_FS
 	tristate "F2FS filesystem support"
 	depends on BLOCK
 	select CRYPTO
-	select KEYS
 	select CRYPTO_CRC32
 	help
 	  F2FS is based on Log-structured File System (LFS), which supports

fs/f2fs/namei.c

@@ -1014,9 +1014,6 @@ static const char *f2fs_encrypted_follow_link(struct dentry *dentry, void **cook
 	u32 max_size = inode->i_sb->s_blocksize;
 	int res;
 
-	if (!dentry)
-		return ERR_PTR(-ECHILD);
-
 	res = fscrypt_get_encryption_info(inode);
 	if (res)
 		return ERR_PTR(res);