Add pyphosphor requirement to rest-dbus

Once this happens the duplicated code can be removed from rest-dbus.
diff --git a/common/recipes-phosphor/rest-dbus/rest-dbus.bb b/common/recipes-phosphor/rest-dbus/rest-dbus.bb
index fa551f5..1dfe027 100644
--- a/common/recipes-phosphor/rest-dbus/rest-dbus.bb
+++ b/common/recipes-phosphor/rest-dbus/rest-dbus.bb
@@ -13,7 +13,7 @@
         python-json \
         python-dbus \
         python-xml \
-        obmc-mapper \
+        pyphosphor \
         "
 
 SRC_URI += " \