zybo-linux-bd.bb: Update to use xilinx-platform-init.bbclass
zybo-linux-bd.bb: Update to use xilinx-platform-init.bbclass

Update this recipe to use the new class, and change the virtual provider
to the more generic 'virtual/xilinx-platform-init'.

Additionally simplify the FILES_${PN}-platform-init paths, and take
advantage of the PLATFORM_INIT_FILES variable.

Signed-off-by: Nathan Rossi <2e8aa918660411855c6d44d5bb2da677aa033255@nathanrossi.com>

Xilinx/meta-xilinx,nathanrossi/meta-xilinx,nathanrossi/meta-xilinx,Xilinx/meta-xilinx,Xilinx/meta-xilinx,nathanrossi/meta-xilinx,Xilinx/meta-xilinx,nathanrossi/meta-xilinx,Xilinx/meta-xilinx,Xilinx/meta-xilinx