Blackfin arch: split board selection off into mach subdirs

Signed-off-by: Mike Frysinger <michael.frysinger@analog.com>
Signed-off-by: Bryan Wu <bryan.wu@analog.com>

diff --git a/arch/blackfin/mach-bf561/Kconfig b/arch/blackfin/mach-bf561/Kconfig
index 0a17c4c..3f48954 100644
--- a/arch/blackfin/mach-bf561/Kconfig
+++ b/arch/blackfin/mach-bf561/Kconfig
@@ -1,4 +1,6 @@
-if BF561
+if (BF561)
+
+source "arch/blackfin/mach-bf561/boards/Kconfig"
 
 menu "BF561 Specific Configuration"