spi: Fix zynq SPI binding

Zynq is using Cadence IP where binding is documented in the Linux kernel
and there is no reason to use different binding.
Synchronize it.

Signed-off-by: Michal Simek <michal.simek@xilinx.com>

drivers/spi/zynq_spi.c

@@ -309,7 +309,7 @@ static const struct dm_spi_ops zynq_spi_ops = {
 };
 
 static const struct udevice_id zynq_spi_ids[] = {
-	{ .compatible = "xlnx,zynq-spi" },
+	{ .compatible = "xlnx,zynq-spi-r1p6" },
 	{ }
 };