ARM: zynq: drop legacy ps7_init.c/h support

We are about to change the location for ps7_init files, breaking the
current work-flows.  It is good time to drop the legacy ps7_init.c/h
support.

Going forward, please use ps7_init_gpl.c/h all the time.
If you are still using old Xilinx tools that are only able to
generate ps7_init.c/h, rename them into ps7_init_gpl.c/h.

Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com>
Suggested-by: Sören Brinkmann <soren.brinkmann@xilinx.com>
Signed-off-by: Michal Simek <michal.simek@xilinx.com>