arm64: dts: agilex: Add SysMgr to Ethernet nodes

[backport 'commit 83d36d212c23 ("arm64: dts: agilex: Add SysMgr
				 to Ethernet nodes")']
from dinguyen/linux/for_next_v5.5_socfpga_dts_v2

Ethernet needs the System Manager to setup the low-level
interface and PHY.

Signed-off-by: Thor Thayer <thor.thayer@linux.intel.com>
Signed-off-by: Dinh Nguyen <dinguyen@kernel.org>
1 file changed