devlink: Expose port function commands to control RoCE

Expose port function commands to enable / disable RoCE, this is used to
control the port RoCE device capabilities.

When RoCE is disabled for a function of the port, function cannot create
any RoCE specific resources (e.g GID table).
It also saves system memory utilization. For example disabling RoCE enable a
VF/SF saves 1 Mbytes of system memory per function.

Example of a PCI VF port which supports function configuration:
Set RoCE of the VF's port function.

$ devlink port show pci/0000:06:00.0/2
pci/0000:06:00.0/2: type eth netdev enp6s0pf0vf1 flavour pcivf pfnum 0
vfnum 1
    function:
        hw_addr 00:00:00:00:00:00 roce enable

$ devlink port function set pci/0000:06:00.0/2 roce disable

$ devlink port show pci/0000:06:00.0/2
pci/0000:06:00.0/2: type eth netdev enp6s0pf0vf1 flavour pcivf pfnum 0
vfnum 1
    function:
        hw_addr 00:00:00:00:00:00 roce disable

Signed-off-by: Shay Drory <shayd@nvidia.com>
Reviewed-by: Jiri Pirko <jiri@nvidia.com>
Signed-off-by: Jakub Kicinski <kuba@kernel.org>