mx31pdk: Convert CONFIG_MX31 flag to use Kconfig.

Move CONFIG_MX31 from mx31pdk.h to mx31pdk_defconfig and introduce
necessary Kconfig changes as well.

Signed-off-by: Magnus Lilja <lilja.magnus@gmail.com>
Reviewed-by: Tom Rini <trini@konsulko.com>
diff --git a/arch/arm/Kconfig b/arch/arm/Kconfig
index c9d6e0a..923fa49 100644
--- a/arch/arm/Kconfig
+++ b/arch/arm/Kconfig
@@ -497,13 +497,6 @@
 	select SUPPORT_SPL
 	select PL011_SERIAL
 
-config TARGET_MX31PDK
-	bool "Support mx31pdk"
-	select BOARD_LATE_INIT
-	select CPU_ARM1136
-	select SUPPORT_SPL
-	select BOARD_EARLY_INIT_F
-
 config TARGET_WOODBURN
 	bool "Support woodburn"
 	select CPU_ARM1136
@@ -665,6 +658,10 @@
 	select PL011_SERIAL
 	select SUPPORT_SPL
 
+config ARCH_MX31
+	bool "NXP i.MX31 family"
+	select CPU_ARM1136
+
 config ARCH_MX7ULP
         bool "NXP MX7ULP"
 	select CPU_V7A
@@ -1305,6 +1302,8 @@
 
 source "arch/arm/mach-imx/mx2/Kconfig"
 
+source "arch/arm/mach-imx/mx3/Kconfig"
+
 source "arch/arm/mach-imx/mx5/Kconfig"
 
 source "arch/arm/mach-imx/mx6/Kconfig"
@@ -1392,7 +1391,6 @@
 source "board/freescale/ls1012aqds/Kconfig"
 source "board/freescale/ls1012ardb/Kconfig"
 source "board/freescale/ls1012afrdm/Kconfig"
-source "board/freescale/mx31pdk/Kconfig"
 source "board/freescale/mx35pdk/Kconfig"
 source "board/freescale/s32v234evb/Kconfig"
 source "board/gdsys/a38x/Kconfig"