mlxsw: Remove Mellanox SwitchIB ASIC support

Initial support for the Mellanox SwitchIB and SwitchIB-2 ASICs was added
in October 2016, but since then development of this driver stopped.
Therefore, the driver does not support any offloads and simply registers
devlink ports for its front panel ports, rendering it irrelevant for
deployment.

Given the driver is not used by any users and that there is no intention
of investing in its development, remove it from the kernel.

Signed-off-by: Amit Cohen <amcohen@nvidia.com>
Signed-off-by: Ido Schimmel <idosch@nvidia.com>
Reviewed-by: Jiri Pirko <jiri@nvidia.com>
Signed-off-by: David S. Miller <davem@davemloft.net>