RDMA/cxgb4: Address sparse warnings

Fixe the following types of sparse warnings
- cast to pointer from integer of different size
- cast from pointer to integer of different size
- incorrect type in assignment (different base types)
- incorrect type in argument 1 (different base types)
- cast from restricted __be64
- cast from restricted __be32

Signed-off-by: Vipul Pandya <vipul@chelsio.com>
Signed-off-by: Roland Dreier <roland@purestorage.com>