arm: mvebu: Move SoC selection (A38X vs AXP) into Kconfig

Until now, the SoC selection for the ARCH_MVEBU platforms has been done
in the config header. Using CONFIG_ARMADA_XP in a non-clear way. As
it needed to get selected for AXP and A38x based boards. This patch
now changes this to move the SoC selection to Kconfig. And also
uses CONFIG_ARCH_MVEBU as a common define for both AXP and A38x.
This makes things a bit clearer - especially for new board additions.

Additionally the defines CONFIG_SYS_MVEBU_DDR_AXP and
CONFIG_SYS_MVEBU_DDR_A38X are replaced with the already available
CONFIG_ARMADA_38X and CONFIG_ARMADA_XP.

And CONFIG_DDR3 is removed, as its not referenced anywhere.

Signed-off-by: Stefan Roese <sr@denx.de>
Cc: Luka Perkov <luka.perkov@sartura.hr>
diff --git a/arch/arm/mach-mvebu/Kconfig b/arch/arm/mach-mvebu/Kconfig
index 9f4d46b..d96b2ae 100644
--- a/arch/arm/mach-mvebu/Kconfig
+++ b/arch/arm/mach-mvebu/Kconfig
@@ -1,20 +1,30 @@
 if ARCH_MVEBU
 
+config ARMADA_38X
+	bool
+
+config ARMADA_XP
+	bool
+
 choice
 	prompt "Marvell MVEBU (Armada XP/38x) board select"
 	optional
 
 config TARGET_CLEARFOG
 	bool "Support ClearFog"
+	select ARMADA_38X
 
 config TARGET_DB_88F6820_GP
 	bool "Support DB-88F6820-GP"
+	select ARMADA_38X
 
 config TARGET_DB_MV784MP_GP
 	bool "Support db-mv784mp-gp"
+	select ARMADA_XP
 
 config TARGET_MAXBCM
 	bool "Support maxbcm"
+	select ARMADA_XP
 
 endchoice