sys: pioctl_nt translate WinErr to Unix

When reading the result of a pioctl fails with ERROR_NOT_SUPPORTED
this must be translated to an EINVAL errno.

Change-Id: I3db03f80b8a0da5d7e4931dc5673c7010d580d8d
Reviewed-on: http://gerrit.openafs.org/11417
Tested-by: BuildBot <buildbot@rampaginggeek.com>
Reviewed-by: Jeffrey Altman <jaltman@your-file-system.com>