arm: zynq: Rename XPSS_ prefix to ZYNQ_ for hardcoded SoC addresses

XPSS prefix was used in past and it is obsolete for quite
some time. Let's use correct SoC name which is Zynq.

Signed-off-by: Michal Simek <michal.simek@xilinx.com>
Reviewed-by: Tom Rini <trini@ti.com>