net/mlx5: Dump of fw_fatal use updated devlink binary interface

Remove redundant code from fw_fatal reporter's dump callback. Use
updated devlink interface of binary fmsg pair which breaks the output
into chunks internally.

Signed-off-by: Aya Levin <ayal@mellanox.com>
Acked-by: Jiri Pirko <jiri@mellanox.com>
Acked-by: Saeed Mahameed <saeedm@mellanox.com>
Signed-off-by: David S. Miller <davem@davemloft.net>