staging: nvec: Reject incomplete messages

Reject incomplete messages, causing the request to be
transmitted again. This should fix various problems
out there.

Signed-off-by: Julian Andres Klode <jak@jak-linux.org>
Acked-by: Marc Dietrich <marvin24@gmx.de>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>