net: phy: mediatek: remove PHY mode check on MT7531

The function mt7531_phy_mode_supported in the DSA driver set supported
mode to PHY_INTERFACE_MODE_GMII instead of PHY_INTERFACE_MODE_INTERNAL
for the internal PHY, so this check breaks the PHY initialization:

mt7530 mdio-bus:00 wan (uninitialized): failed to connect to PHY: -EINVAL

Remove the check to make it work again.

Reported-by: Hauke Mehrtens <hauke@hauke-m.de>
Fixes: e40d2cca

 ("net: phy: add MediaTek Gigabit Ethernet PHY driver")
Signed-off-by: DENG Qingfang <dqfext@gmail.com>
Acked-by: Arınç ÜNAL <arinc.unal@arinc9.com>
Tested-by: Hauke Mehrtens <hauke@hauke-m.de>
Signed-off-by: David S. Miller <davem@davemloft.net>