arm: zynq: Get rid of xilinx function prefix

Xilinx is vendor name not SoC name. Use zynq instead.

Also remove one checkpatch warning:
WARNING: static const char * array should probably be
static const char * const
+static const char *xilinx_dt_match[] = {

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