libxc/NetBSD: return ioctl return value on error

NetBSD libxc hypercall implementation was returning -errno on error,
instead of the actual error value from ioctl. Returning error is
easier to understand, and the caller can always check errno.

Signed-off-by: Roger Pau Monne <roger.pau@entel.upc.edu>
Acked-by: Ian Campbell <ian.campbell.com>
Committed-by: Ian Jackson <ian.jackson.citrix.com>
Reported-by: Olaf Hering <olaf@aepfle.de>

tools/libxc/xc_netbsd.c

@@ -103,7 +103,7 @@ static int netbsd_privcmd_hypercall(xc_interface *xch, xc_osdep_handle h, privcm
      * implementation.
      */
     if (error < 0)
-        return -errno;
+        return error;
     else
         return hypercall->retval;
 }