RDMA/mlx5: Delete unused mlx5_ib_copy_pas prototype

mlx5_ib_copy_pas() doesn't exist anymore.

Signed-off-by: Alexey Dobriyan <adobriyan@gmail.com>
Link: https://lore.kernel.org/r/a2cb861e-d11e-4567-8a73-73763d1dc199@p183


Signed-off-by: Leon Romanovsky <leon@kernel.org>