staging: nvec: ps2: tell nvec to send 6 byte long messages

This packet size used on most modern touchpads. Ideally, this should
be configurable or autodetected.

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