net: sparx5: activate FDMA tx in start()

The function sparx5_fdma_tx_activate() is responsible for configuring
the TX FDMA instance and activating the channel. TX activation has
previously been done in the xmit() function, when the first frame is
transmitted. Now that we have separate functions for starting and
stopping the FDMA, it seems reasonable to move the TX activation to the
start function. This change has no implications on the functionality.

Reviewed-by: Steen Hegelund <Steen.Hegelund@microchip.com>
Signed-off-by: Daniel Machon <daniel.machon@microchip.com>
Link: https://patch.msgid.link/20250113-sparx5-lan969x-switch-driver-5-v2-3-c468f02fd623@microchip.com


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