net: cosa: add necessary () to macro argument

Macro argument 'cosa' may be better as '(cosa)' to avoid
precedence issues.

Signed-off-by: Peng Li <lipeng321@huawei.com>
Signed-off-by: Guangbin Huang <huangguangbin2@huawei.com>
Signed-off-by: David S. Miller <davem@davemloft.net>