[roll] Roll fuchsia [wlan] Reduce wire usage in brcmfmac Sim tests.

Use natural FIDL types instead of wire types when storing FIDL messages
inside these two Sim tests. A few minor cleanups (using const, etc.) are
included. This change does not affect any non-test code.

Test: fx test brcmfmac_sim_test
Original-Reviewed-on: https://fuchsia-review.googlesource.com/c/fuchsia/+/1158116
Original-Revision: 2a15f2a46de3492dae5cdcf87e59a1b6b659beea
GitOrigin-RevId: 43d903676075f09b9e19857492c7455643156585
Change-Id: I24ee8d7b649e05a6501b47ecd14df29f23be1007
diff --git a/stem b/stem
index 9dc3a74..d72cebf 100644
--- a/stem
+++ b/stem
@@ -11,7 +11,7 @@
              githooks="integration/git-hooks"
              remote="https://fuchsia.googlesource.com/fuchsia"
              gerrithost="https://fuchsia-review.googlesource.com"
-             revision="0eb9607acefce9025670600cf06a82cf1b81c98a"/>
+             revision="2a15f2a46de3492dae5cdcf87e59a1b6b659beea"/>
   </projects>
   <hooks>
     <hook name="install-environment"