[third_party/pigweed] Roll 2 commits

ddbc9fc7f5c601a third_party/nanopb: Detect protoc updates
a2dd3fbd45269c8 pw_allocator: Refactor SplitFreeListAllocator to u

https://pigweed.googlesource.com/pigweed/pigweed
third_party/pigweed Rolled-Commits: 556c19d670b9dc4..ddbc9fc7f5c601a
Roller-URL: https://ci.chromium.org/b/8766242545099407345
GitWatcher: ignore
CQ-Do-Not-Cancel-Tryjobs: true
Change-Id: I55b94db93180e877ff6a2b7109f2dd843ac4c97a
Reviewed-on: https://pigweed-review.googlesource.com/c/pigweed/kudzu/+/177703
Commit-Queue: Pigweed Roller <pigweed-roller@pigweed-service-accounts.iam.gserviceaccount.com>
Bot-Commit: Pigweed Roller <pigweed-roller@pigweed-service-accounts.iam.gserviceaccount.com>
diff --git a/third_party/pigweed b/third_party/pigweed
index 556c19d..ddbc9fc 160000
--- a/third_party/pigweed
+++ b/third_party/pigweed
@@ -1 +1 @@
-Subproject commit 556c19d670b9dc4a0044a4a7c8ddae6cc0353a66
+Subproject commit ddbc9fc7f5c601ab417db37e02cbe5294f21ad6d