generic/395: remove workarounds for wrong error codes

generic/395: remove workarounds for wrong error codes

generic/395 contains workarounds to allow for some of the fscrypt ioctls
to fail with different error codes.  However, the error codes were all
fixed up and documented years ago:

- FS_IOC_GET_ENCRYPTION_POLICY on ext4 failed with ENOENT instead of
  ENODATA on unencrypted files.  Fixed by commit db717d8e26c2
  ("fscrypto: move ioctl processing more fully into common code").

- FS_IOC_SET_ENCRYPTION_POLICY failed with EINVAL instead of EEXIST
  on encrypted files.  Fixed by commit 8488cd96ff88 ("fscrypt: use
  EEXIST when file already uses different policy").

- FS_IOC_SET_ENCRYPTION_POLICY failed with EINVAL instead of ENOTDIR
  on nondirectories.  Fixed by commit dffd0cfa06d4 ("fscrypt: use
  ENOTDIR when setting encryption policy on nondirectory").

It's been long enough, so update the test to expect the correct behavior
only, so we don't accidentally reintroduce the wrong behavior.

Signed-off-by: Eric Biggers <ebiggers@google.com>
Signed-off-by: Eryu Guan <guaneryu@gmail.com>