net: dsa: microchip: lan937x: Add error handling in lan937x_setup

Introduce error handling for lan937x_cfg function calls in lan937x_setup.
This change ensures that if any lan937x_cfg or ksz_rmw32 calls fails, the
function will return the appropriate error code.

Signed-off-by: Oleksij Rempel <o.rempel@pengutronix.de>
Acked-by: Arun Ramadoss <arun.ramadoss@microchip.com>
Link: https://patch.msgid.link/20240703083820.3152100-1-o.rempel@pengutronix.de


Signed-off-by: Paolo Abeni <pabeni@redhat.com>