wifi(interface): Use the "bitfield" type for masks

Change all the variables representing masks to the new bitfield type
in all the Wifi HIDL interfaces.
The generated code will still produce the underlying type of enum as
param. So, no changes are needed in the implementation.

Bug: 33358724
Test: Compiles
Change-Id: Id2e5dee2ce1f1ec8e744aa1c81d3cb9c66e7fc39
diff --git a/wifi/1.0/IWifiStaIface.hal b/wifi/1.0/IWifiStaIface.hal
index 7dad8af..6a738a9 100644
--- a/wifi/1.0/IWifiStaIface.hal
+++ b/wifi/1.0/IWifiStaIface.hal
@@ -120,7 +120,9 @@
    *         |WifiStatusCode.ERROR_UNKNOWN|
    * @return capabilities Bitset of |StaIfaceCapabilityMask| values.
    */
-  getCapabilities() generates (WifiStatus status, uint32_t capabilities);
+  getCapabilities()
+      generates (WifiStatus status,
+                 bitfield<StaIfaceCapabilityMask> capabilities);
 
   /**
    * Used to query additional information about the chip's APF capabilities.