arm64: dts: zynqmp: Add DDRC node

Add ddrc memory controller node in dts. The size mentioned in dts is
0x30000, because we need to access DDR_QOS INTR registers located at
0xFD090208 from this driver.

Signed-off-by: Manish Narani <manish.narani@xilinx.com>
Signed-off-by: Michal Simek <michal.simek@xilinx.com>