RDMA/mlx5: Fix query_srq_cmd() function

RDMA/mlx5: Fix query_srq_cmd() function

The output buffer used in mlx5_cmd_exec_inout() was wrongly changed from
pre-allocated srq_out pointer to an input "out" point. That leads to
unpredictable results in the get_srqc() call later.

Fixes: 5f6541f54dce ("RDMA/mlx5: Update mlx5_ib to use new cmd interface")
Link: https://lore.kernel.org/r/20200513100809.246315-1-leon@kernel.org
Reported-by: Dan Carpenter <dan.carpenter@oracle.com>
Signed-off-by: Leon Romanovsky <leonro@mellanox.com>
Signed-off-by: Jason Gunthorpe <jgg@mellanox.com>