net: dsa: felix: make vsc9959_tas_guard_bands_update() visible to ocelot->ops

In a future change we will need to make
ocelot_port_update_active_preemptible_tcs() call
vsc9959_tas_guard_bands_update(), but that is currently not possible,
since the ocelot switch lib does not have access to functions private to
the DSA wrapper.

Move the pointer to vsc9959_tas_guard_bands_update() from felix->info
(which is private to the DSA driver) to ocelot->ops (which is also
visible to the ocelot switch lib).

Signed-off-by: Vladimir Oltean <vladimir.oltean@nxp.com>
Message-ID: <20230705104422.49025-3-vladimir.oltean@nxp.com>
Signed-off-by: Jakub Kicinski <kuba@kernel.org>