MIPS: Loongson32: Fix PHY-mode being left unspecified

MIPS: Loongson32: Fix PHY-mode being left unspecified

commit 0da4b6760919 ("net: stmmac: implement support for passive mode
converters via dt") has changed the plat->interface field semantics from
containing the PHY-mode to specifying the MAC-PCS interface mode. Due to
that the loongson32 platform code will leave the phylink interface
uninitialized with the PHY-mode intended by the means of the actual
platform setup. The commit-author most likely has just missed the
arch-specific code to fix. Let's mend the Loongson32 platform code then by
assigning the PHY-mode to the phy_interface field of the STMMAC platform
data.

Fixes: 0da4b6760919 ("net: stmmac: implement support for passive mode converters via dt")
Signed-off-by: Serge Semin <Sergey.Semin@baikalelectronics.ru>
Signed-off-by: Keguang Zhang <keguang.zhang@gmail.com>
Tested-by: Keguang Zhang <keguang.zhang@gmail.com>
Signed-off-by: Thomas Bogendoerfer <tsbogend@alpha.franken.de>