arm64: dts: imx8mp-phycore-som: Remove eth phy interrupt

In some occasions the ethernet phy IRQ can not be detected correctly
by the SoC. This leads to a non detected link in Linux. The problem is
caused by the buffer that adjusts the voltage between ethernet phy
and SoC. To workaround this, remove the IRQ support for the ethernet
phy and use polling instead.

Signed-off-by: Christian Hemp <c.hemp@phytec.de>
Signed-off-by: Teresa Remmet <t.remmet@phytec.de>
Signed-off-by: Shawn Guo <shawnguo@kernel.org>