RDMA/i40iw: Replace atomic_add_return(1, ..)

atomic_inc_return() is a little neater

Link: https://lore.kernel.org/r/1606726376-7675-1-git-send-email-yejune.deng@gmail.com


Signed-off-by: Yejune Deng <yejune.deng@gmail.com>
Signed-off-by: Jason Gunthorpe <jgg@nvidia.com>