ARM: zynq: Simplify zynq configuration

Extending Kconfig for adding new platform is a lot of work
for nothing. Setting SYS_CONFIG_NAME directly in Kconfig and
remove all dependencies on TARGET_ZYNQ_* options including SPL.
As a side-effect it also remove custom init folder for ps7_init_gpl.*
files. Folder is chosen based on device-tree file.

Signed-off-by: Michal Simek <michal.simek@xilinx.com>
diff --git a/board/xilinx/zynq/Makefile b/board/xilinx/zynq/Makefile
index eab9303..7de0212 100644
--- a/board/xilinx/zynq/Makefile
+++ b/board/xilinx/zynq/Makefile
@@ -7,17 +7,7 @@
 
 obj-y	:= board.o
 
-# Copied from Xilinx SDK 2014.4
-hw-platform-$(CONFIG_TARGET_ZYNQ_ZED)		:= zed_hw_platform
-hw-platform-$(CONFIG_TARGET_ZYNQ_MICROZED)	:= MicroZed_hw_platform
-hw-platform-$(CONFIG_TARGET_ZYNQ_ZC702)		:= ZC702_hw_platform
-hw-platform-$(CONFIG_TARGET_ZYNQ_ZC706)		:= ZC706_hw_platform
-hw-platform-$(CONFIG_TARGET_ZYNQ_ZYBO)		:= zybo_hw_platform
-# If you want to use customized ps7_init_gpl.c/h,
-# enable CONFIG_ZYNQ_CUSTOM_INIT and put them into custom_hw_platform/.
-# This line must be placed at the bottom of the list because
-# it takes precedence over the default ones.
-hw-platform-$(CONFIG_ZYNQ_CUSTOM_INIT)		:= custom_hw_platform
+hw-platform-y :=$(shell echo $(CONFIG_DEFAULT_DEVICE_TREE))
 
 init-objs := $(if $(wildcard $(srctree)/$(src)/$(hw-platform-y)/ps7_init_gpl.c),\
 	$(hw-platform-y)/ps7_init_gpl.o)