arm: mvebu: Move Armada XP/38x Kconfig to mach specific Kconfig file

Introduce a mach-mvebu/Kconfig for all Armada based SoC's.

Signed-off-by: Stefan Roese <sr@denx.de>
diff --git a/configs/maxbcm_defconfig b/configs/maxbcm_defconfig
index b0b0d6c..5957997 100644
--- a/configs/maxbcm_defconfig
+++ b/configs/maxbcm_defconfig
@@ -1,4 +1,5 @@
 CONFIG_ARM=y
+CONFIG_ARCH_MVEBU=y
 CONFIG_TARGET_MAXBCM=y
 CONFIG_SPL=y
 # CONFIG_CMD_IMLS is not set