net: stmmac: sunxi: use devm_stmmac_pltfr_probe()

Using devm_stmmac_pltfr_probe() simplifies the probe function. This
will not only call plat_dat->init (sun7i_dwmac_init), but also
plat_dat->exit (sun7i_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>
Link: https://patch.msgid.link/E1u4fre-000nMr-FT@rmk-PC.armlinux.org.uk


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