ext4: make error code in __ext4fs_dirhash() consistent.

Currently __ext4fs_dirhash() returns -1 (-EPERM) if fscrypt doesn't
have encryption key, which may confuse users. Make the error code here
consistent with existing error code.

Signed-off-by: Julian Sun <[e-mail]>
Message-ID: <[e-mail]>
Signed-off-by: Theodore Ts'o <[e-mail]>

fs/ext4/hash.c

···
 			combined_hash = fscrypt_fname_siphash(dir, &qname);
 		} else {
 			ext4_warning_inode(dir, "Siphash requires key");
-			return -1;
+			return -EINVAL;
 		}
 
 		hash = (__u32)(combined_hash >> 32);