arm64: dts: zynqmp: Enable USB2.0 for zc1751-xm016-dc2

The board zynqmp-zc1751-xm016-dc2 support only USB2.0.
This patch removes USB3.0 DT configuration for DC2 board.

Signed-off-by: Piyush Mehta <piyush.mehta@xilinx.com>
Signed-off-by: Michal Simek <michal.simek@xilinx.com>