Fix getdents default error code

Cargo.lock

@@ -27,7 +27,7 @@ dependencies = [
 
 [[package]]
 name = "redox-scheme"
-version = "0.2.1"
+version = "0.2.2"
 dependencies = [
  "libredox",
  "redox_syscall",

src/scheme_mut.rs

@@ -171,7 +171,7 @@ pub trait SchemeMut {
         buf: DirentBuf<&'buf mut [u8]>,
         opaque_offset: u64,
     ) -> Result<DirentBuf<&'buf mut [u8]>> {
-        Err(Error::new(EBADF))
+        Err(Error::new(EOPNOTSUPP))
     }
 
     #[allow(unused_variables)]