net: stmmac: dwc-qos: Make struct dwc_eth_dwmac_data::remove return void

net: stmmac: dwc-qos: Make struct dwc_eth_dwmac_data::remove return void

All implementations of the remove callback return 0 unconditionally. So
in dwc_eth_dwmac_remove() there is no error handling necessary. Simplify
accordingly.

This is a preparation for making struct platform_driver::remove return
void, too.

Signed-off-by: Uwe Kleine-König <u.kleine-koenig@pengutronix.de>
Link: https://lore.kernel.org/r/20230211112431.214252-2-u.kleine-koenig@pengutronix.de
Signed-off-by: Jakub Kicinski <kuba@kernel.org>