fscrypt: drop empty name check from fname_decrypt()

fname_decrypt() is validating that the encrypted filename is nonempty.
However, earlier a stronger precondition was already enforced: the
encrypted filename must be at least 16 (FS_CRYPTO_BLOCK_SIZE) bytes.

Drop the redundant check for an empty filename.
Signed-off-by: Eric Biggers <ebiggers@google.com>
Signed-off-by: Theodore Ts'o <tytso@mit.edu>

fs/crypto/fname.c

@@ -97,9 +97,6 @@ static int fname_decrypt(struct inode *inode,
 	int res = 0;
 	char iv[FS_CRYPTO_BLOCK_SIZE];
 
-	if (iname->len <= 0)
-		return -EIO;
-
 	/* Allocate request */
 	req = skcipher_request_alloc(tfm, GFP_NOFS);
 	if (!req)