arm64: dts: stratix10: Add SDRAM node

Add the SDRAM node to follow the Arria10 layout and bindings. The
Arria10 SDRAM functions expect this node.

Signed-off-by: Thor Thayer <thor.thayer@linux.intel.com>
Signed-off-by: Borislav Petkov <bp@suse.de>
Acked-by: Dinh Nguyen <dinguyen@kernel.org>
Cc: robh+dt@kernel.org
Cc: mark.rutland@arm.com
Cc: mchehab@kernel.org
Cc: devicetree@vger.kernel.org
Cc: linux-edac@vger.kernel.org
Link: https://lkml.kernel.org/r/1537883342-30180-4-git-send-email-thor.thayer@linux.intel.com