ARM: zynq: DT: Migrate UART to Cadence binding

The Zynq UART is Cadence IP and the driver has been renamed accordingly.
Migrate the DT to use the new binding for the UART driver.

Signed-off-by: Soren Brinkmann <soren.brinkmann@xilinx.com>
Acked-by: Peter Crosthwaite <peter.crosthwaite@xilinx.com>
Acked-by: Rob Herring <robh@kernel.org>
Tested-by: Michal Simek <michal.simek@xilinx.com>
Signed-off-by: Michal Simek <michal.simek@xilinx.com>
(cherry picked from commit 271b35d5c200d69d5fb317a976c8f24383c929a7)