ARM: zynq: DT: Clarify Xilinx Zynq platform

ep107 was emulation platform and compatible string
have been changed long time ago.

"ARM: zynq: dts: split up device tree"
(sha1: e06f1a9ed7ebff170ba05d2606d079fb36c6a52d)

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