RDMA/cxgb4: Fix missing parentheses

Parens are missing: '|' has a higher presedence than '?'.

Signed-off-by: Roel Kluin <roel.kluin@gmail.com>
Acked-by: Steve Wise <swise@opengridcomputing.com>
Signed-off-by: Roland Dreier <roland@purestorage.com>