ARM: multi_v7_defconfig: enable ARM_ATAG_DTB_COMPAT

Without this, legacy platforms that can boot with a multiplatform
kernel but that need the DTB to be appended, won't have a way to pass
firmware-set bootargs to the kernel.

This is needed to boot multi_v7_defconfig on snowball, for instance.

Signed-off-by: Olof Johansson <olof@lixom.net>
diff --git a/arch/arm/configs/multi_v7_defconfig b/arch/arm/configs/multi_v7_defconfig
index 6e572c6..aba4ec7 100644
--- a/arch/arm/configs/multi_v7_defconfig
+++ b/arch/arm/configs/multi_v7_defconfig
@@ -46,6 +46,7 @@
 CONFIG_SMP=y
 CONFIG_HIGHPTE=y
 CONFIG_ARM_APPENDED_DTB=y
+CONFIG_ARM_ATAG_DTB_COMPAT=y
 CONFIG_NET=y
 CONFIG_UNIX=y
 CONFIG_INET=y