RDMA/cxgb3: Use sizeof() notation instead of plain sizeof

sizeof(a), sizeof a and sizeof (a) are all valid notations, but first is
more readable format recommended by checkpatch.pl.

Let's canonize it in cxgb3 drivers, so latter patches won't emit
checkpatch warnings. As part of this change, a redundant memset() was
removed.

Signed-off-by: Leon Romanovsky <leonro@mellanox.com>
Signed-off-by: Jason Gunthorpe <jgg@mellanox.com>