RDMA/mlx5: Fix memory leak in mlx5_ib_create_srq() error path

Fix memory leak in the error path of mlx5_ib_create_srq() by making sure
to free the allocated srq.

Fixes: c2b37f76 ("IB/mlx5: Fix integer overflows in mlx5_ib_create_srq")
Signed-off-by: Kamal Heib <kamalheib1@gmail.com>
Acked-by: Leon Romanovsky <leonro@mellanox.com>
Signed-off-by: Jason Gunthorpe <jgg@mellanox.com>