Input: zforce - don't overwrite the stack

If we get a corrupted packet with PAYLOAD_LENGTH > FRAME_MAXSIZE, we
will silently overwrite the stack.

Cc: stable@vger.kernel.org
Signed-off-by: Oleksij Rempel <external.Oleksij.Rempel@de.bosch.com>
Signed-off-by: Dirk Behme <dirk.behme@de.bosch.com>
Signed-off-by: Dmitry Torokhov <dmitry.torokhov@gmail.com>