microblaze: Add support for device tree driven board configuration

This is minimum code required to be able to use device-tree
for u-boot initialization.
Currently only for device driver initialization.

Linker script change ensures DTB to be aligned
for both options CONFIG_OF_EMBED and CONFIG_OF_SEPARATE.

Signed-off-by: Michal Simek <monstr@monstr.eu>
Acked-by: Stephan Linz <linz@li-pro.net>
CC: Simon Glass <sjg@chromium.org>
diff --git a/arch/microblaze/config.mk b/arch/microblaze/config.mk
index aca79e2..b4935f0 100644
--- a/arch/microblaze/config.mk
+++ b/arch/microblaze/config.mk
@@ -31,3 +31,5 @@
 PLATFORM_CPPFLAGS += -ffixed-r31 -D__microblaze__
 
 LDSCRIPT ?= $(SRCTREE)/$(CPUDIR)/u-boot.lds
+
+CONFIG_ARCH_DEVICE_TREE := microblaze