ARM: dts: imx6: Use gpc for FEC interrupt controller to fix wake on LAN.

In order to wake from suspend by ethernet magic packets the GPC
must be used as intc does not have wakeup functionality.

But the FEC DT node currently uses interrupt-extended,
specificying intc, thus breaking WoL.

This problem is probably fallout from the stacked domain conversion
as intc used to chain to GPC.

So replace "interrupts-extended" by "interrupts" to use the default
parent which is GPC.

Fixes: b923ff6a

 ("ARM: imx6: convert GPC to stacked domains")

Signed-off-by: Martin Fuzzey <martin.fuzzey@flowbird.group>
Signed-off-by: David S. Miller <davem@davemloft.net>