arm: imx: mx23: Move MX23 selection to Kconfig

The motivation for moving MX23 selection to Kconfig is to be able
to better handle NAND MXS selection through Kconfig.

This selection method also aligns with the way other i.MX SoCs are
selected in U-Boot.

Signed-off-by: Stefan Agner <stefan.agner@toradex.com>
diff --git a/arch/arm/mach-imx/mxs/Kconfig b/arch/arm/mach-imx/mxs/Kconfig
new file mode 100644
index 0000000..f984545
--- /dev/null
+++ b/arch/arm/mach-imx/mxs/Kconfig
@@ -0,0 +1,35 @@
+if ARCH_MX23
+
+config MX23
+	bool
+	default y
+
+choice
+	prompt "MX23 board select"
+	optional
+
+config TARGET_MX23_OLINUXINO
+	bool "Support mx23_olinuxino"
+	select BOARD_EARLY_INIT_F
+
+config TARGET_MX23EVK
+	bool "Support mx23evk"
+	select BOARD_EARLY_INIT_F
+
+config TARGET_SANSA_FUZE_PLUS
+	bool "Support sansa_fuze_plus"
+
+config TARGET_XFI3
+	bool "Support xfi3"
+
+endchoice
+
+config SYS_SOC
+	default "mxs"
+
+source "board/olimex/mx23_olinuxino/Kconfig"
+source "board/freescale/mx23evk/Kconfig"
+source "board/sandisk/sansa_fuze_plus/Kconfig"
+source "board/creative/xfi3/Kconfig"
+
+endif