net/mlx5: FPGA, Use async events chain

Remove the explicit call to mlx5_fpga_event on
MLX5_EVENT_TYPE_FPGA_ERROR or MLX5_EVENT_TYPE_FPGA_QP_ERROR
let fpga core to register its own handler when its ready.

Signed-off-by: Saeed Mahameed <saeedm@mellanox.com>