net: stmmac: dwmac-sun8i: fix allwinner,leds-active-low handling

The driver expect "allwinner,leds-active-low" to be in PHY node, but
the binding doc expect it to be in MAC node.

Since all board DT use it also in MAC node, the driver need to search
allwinner,leds-active-low in MAC node.

Signed-off-by: Corentin Labbe <clabbe.montjoie@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>