ARM64: zynqmp: Select SYS_CONFIG_NAME via Kconfig

This option enable adding new platform suport just by adding defconfig
and DTS file which will target generic configuration for SoC.
Make no sense to extend Kconfig just create a pointer between DTS and
configuration file.

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

arch/arm/cpu/armv8/zynqmp/Kconfig

 if ARCH_ZYNQMP
 
-choice
-	prompt "Xilinx ZynqMP board select"
-
-config TARGET_ZYNQMP_EP
-	bool "ZynqMP EP Board"
-
-endchoice
-
 config SYS_BOARD
 	default "zynqmp"
 
@@ -18,7 +10,12 @@ config SYS_SOC
 	default "zynqmp"
 
 config SYS_CONFIG_NAME
-	default "xilinx_zynqmp_ep" if TARGET_ZYNQMP_EP
+	string "Board configuration name"
+	default "xilinx_zynqmp"
+	help
+	  This option contains information about board configuration name.
+	  Based on this option include/configs/<CONFIG_SYS_CONFIG_NAME>.h header
+	  will be used for board configuration.
 
 config ZYNQMP_USB
 	bool "Configure ZynqMP USB"

configs/xilinx_zynqmp_ep_defconfig

 CONFIG_ARM=y
+CONFIG_SYS_CONFIG_NAME="xilinx_zynqmp_ep"
 CONFIG_ARCH_ZYNQMP=y
 CONFIG_ZYNQMP_USB=y
 CONFIG_SYS_TEXT_BASE=0x8000000