IB/mlx5: Add support for extended atomic operations

Extended atomic operations cmp&swp and fetch&add is a Mellanox
feature extending the standard atomic operation to use, varied
operand sizes, as apposed to normal atomic operation that use
an 8 byte operand only.
Extended atomics allows masking the results and arguments.

This patch configures QP to support extended atomic operation
with the maximum size possible, as exposed by HCA capabilities.

Signed-off-by: Yonatan Cohen <yonatanc@mellanox.com>
Reviewed-by: Guy Levi <guyle@mellanox.com>
Signed-off-by: Leon Romanovsky <leonro@mellanox.com>
Signed-off-by: Doug Ledford <dledford@redhat.com>