Blackfin arch: add board default configs to blackfin arch

Signed-off-by: Mike Frysinger <michael.frysinger@analog.com>
Signed-off-by: Bryan Wu <bryan.wu@analog.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
diff --git a/arch/blackfin/Makefile b/arch/blackfin/Makefile
index 52d4dbd..75e89c3 100644
--- a/arch/blackfin/Makefile
+++ b/arch/blackfin/Makefile
@@ -15,6 +15,7 @@
 CFLAGS_MODULE    += -mlong-calls
 KALLSYMS         += --symbol-prefix=_
 
+KBUILD_DEFCONFIG := BF537-STAMP_defconfig
 
 # setup the machine name and the machine dependent settings
 machine-$(CONFIG_BF531) := bf533