Use bitfield type in GNSS HAL.

Test: mma

Change-Id: I92acf537a489fb06d942d3aa19ec9f40ffe26c23
diff --git a/gnss/1.0/IGnssNiCallback.hal b/gnss/1.0/IGnssNiCallback.hal
index f23b354..a7abad9 100644
--- a/gnss/1.0/IGnssNiCallback.hal
+++ b/gnss/1.0/IGnssNiCallback.hal
@@ -78,7 +78,7 @@
          * Notification/verification options, combinations of GnssNiNotifyFlags
          * constants.
          */
-        GnssNiNotifyFlags notifyFlags;
+        bitfield<GnssNiNotifyFlags> notifyFlags;
 
         /*
          * Timeout period to wait for user response.