arm64: zynqmp: Add support for zynqmp automotive silicons

Remove silicon prefix. Automotive grade devices are using xazu instead
of xczu prefix.

The patch "fpga: xilinx: Check for substring in device ID validation"
(sha1: f7213267)
enables this functionality for zynq devices that only substrings are
checked.
Unfortunately there is no way how to detect device grade that's why
this change is reasonable.

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