net: stmmac: sun8i: use stmmac_pltfr_probe()

Using stmmac_pltfr_probe() simplifies the probe function. This will not
only call plat_dat->init (sun8i_dwmac_init), but also plat_dat->exit
(sun8i_dwmac_exit) appropriately if stmmac_dvr_probe() fails. This
results in an overall simplification of the glue driver.

Signed-off-by: Russell King (Oracle) <rmk+kernel@armlinux.org.uk>
Reviewed-by: Maxime Chevallier <maxime.chevallier@bootlin.com>
Reviewed-by: Andrew Lunn <andrew@lunn.ch>
Tested-by: Corentin Labbe <clabbe.montjoie@gmail.com>
Link: https://patch.msgid.link/E1u4dKb-000dV7-3B@rmk-PC.armlinux.org.uk


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