[third_party/pigweed] Roll 3 commits

ddbc9fc7f5c601a third_party/nanopb: Detect protoc updates
a2dd3fbd45269c8 pw_allocator: Refactor SplitFreeListAllocator to u
556c19d670b9dc4 SEED-0116: Claim SEED number

https://pigweed.googlesource.com/pigweed/pigweed
third_party/pigweed Rolled-Commits: 65ab9e4fde35275..ddbc9fc7f5c601a
Roller-URL: https://ci.chromium.org/b/8766243207558084241
GitWatcher: ignore
CQ-Do-Not-Cancel-Tryjobs: true
Change-Id: I03ed10ab519c540c1f46681b39d29cb5763bd10a
Reviewed-on: https://pigweed-review.googlesource.com/c/pigweed/experimental/+/177718
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 65ab9e4..ddbc9fc 160000
--- a/third_party/pigweed
+++ b/third_party/pigweed
@@ -1 +1 @@
-Subproject commit 65ab9e4fde35275ad7a045e0da6e3342ef524cfc
+Subproject commit ddbc9fc7f5c601ab417db37e02cbe5294f21ad6d