ARM: mx6: move to a standard arch/board approach

Freescale boards are currently all defined in arch/arm/Kconfig, which
makes them hard to detect.
Moreover the MX6 SoC variant (Q, D, DL, S, SL) selection is currently
done via the SYS_EXTRA_OPTIONS option which marked as deprecated.

Move to a more standard way to select sub-architecture and board by
creating a Kconfig under arch/arm/cpu/armv7/mx6 and a new ARCH_MX6
option.

Existing MX6 board definitions should be moved in this new Kconfig in
choice menu, and new boards should be directly declared in this menu.
Signed-off-by: NBoris Brezillon <boris.brezillon@free-electrons.com>

arch/arm/Kconfig

@@ -433,6 +433,10 @@ config ARCH_KEYSTONE
 	select CPU_V7
 	select SUPPORT_SPL
 
+config ARCH_MX6
+	bool "Freescale MX6"
+	select CPU_V7
+
 config TARGET_M53EVK
 	bool "Support m53evk"
 	select CPU_V7
@@ -735,6 +739,8 @@ source "arch/arm/mach-keystone/Kconfig"
 
 source "arch/arm/mach-kirkwood/Kconfig"
 
+source "arch/arm/cpu/armv7/mx6/Kconfig"
+
 source "arch/arm/mach-nomadik/Kconfig"
 
 source "arch/arm/cpu/armv7/omap3/Kconfig"

arch/arm/cpu/armv7/mx6/Kconfig

+if ARCH_MX6
+
+config MX6
+	bool
+	default y
+
+config MX6D
+	bool
+
+config MX6DL
+	bool
+
+config MX6Q
+	bool
+
+config MX6QDL
+	bool
+
+config MX6S
+	bool
+
+config MX6SL
+	bool
+
+config MX6SX
+	bool
+
+config SYS_SOC
+	default "mx6"
+
+endif