net: sparx5: change spx5_wr to spx5_rmw in cal update()

In preparation for lan969x, use spx5_rmw() for enabling the update of
the calendar. This is required to not overwrite the DSM_TAXI_CAL_CFG
register, as an additional write will be added before this one, in a
subsequent patch.

Reviewed-by: Steen Hegelund <Steen.Hegelund@microchip.com>
Signed-off-by: Daniel Machon <daniel.machon@microchip.com>
Link: https://patch.msgid.link/20241024-sparx5-lan969x-switch-driver-2-v2-2-a0b5fae88a0f@microchip.com


Signed-off-by: Jakub Kicinski <kuba@kernel.org>