The fhandler method ftruncate returns either EISDIR if it has been
called on directories, or EINVAL if called on files other than
regular files. This matches what ftruncate(2) is supposed to return,
but it doesn't match posix_fallocate(3), which is supposed to return
ENODEV in both cases.
To accomplish that, return ENODEV from fhandler_base::ftruncate()
and convert it to EINVAL in ftruncate(2). In posix_fallocate(3),
convert EISDIR to ENODEV.
Fixes: 7636b58590 ("* autoload.cc (NtSetInformationFile): Define.")
Signed-off-by: Corinna Vinschen <corinna@vinschen.de>