meta-bletchley: enable obmc-phosphor-buttons feature

Enable obmc-phosphor-buttons and add gpio_defs.json to support the
feature of debug card button.

Signed-off-by: Potin Lai <potin.lai@quantatw.com>
Change-Id: I673db3587232bfc57dabc5fa157ae9945cb25974
diff --git a/meta-facebook/meta-bletchley/recipes-phosphor/images/fb-bletchley-phosphor-image.inc b/meta-facebook/meta-bletchley/recipes-phosphor/images/fb-bletchley-phosphor-image.inc
index c359c5b..b32b28f 100644
--- a/meta-facebook/meta-bletchley/recipes-phosphor/images/fb-bletchley-phosphor-image.inc
+++ b/meta-facebook/meta-bletchley/recipes-phosphor/images/fb-bletchley-phosphor-image.inc
@@ -12,4 +12,6 @@
     phosphor-ipmi-ipmb \
     fb-ipmi-oem \
     board-type-checker \
+    obmc-phosphor-buttons-signals \
+    obmc-phosphor-buttons-handler \
 "