bonding: fix ad_select module param check

Obvious copy/paste error when I converted the ad_select to the new
option API. "lacp_rate" there should be "ad_select" so we can get the
proper value.

CC: Jay Vosburgh <j.vosburgh@gmail.com>
CC: Veaceslav Falico <vfalico@gmail.com>
CC: Andy Gospodarek <andy@greyhouse.net>
CC: David S. Miller <davem@davemloft.net>

Fixes: 9e5f5eeb ("bonding: convert ad_select to use the new option
API")
Reported-by: Karim Scheik <karim.scheik@prisma-solutions.at>
Signed-off-by: Nikolay Aleksandrov <nikolay@redhat.com>
Signed-off-by: David S. Miller <davem@davemloft.net>