RDMA/mlx5: Return an error if copy_to_user fails

In theoretical event, the ib_copy_to_udata() can fail, so return -EFAULT
error to the user, so he will destroy the QP.

Fixes: 50aec2c3 ("RDMA/mlx5: Return ECE data after modify QP")
Link: https://lore.kernel.org/r/20200602125548.172654-2-leon@kernel.org


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