[third_party/pigweed] Roll 3 commits

55b88ef80fc2403 pw_channel: Split open bits for read and write
be2ee681c2c0176 pw_async2: Add PendFuncTask
a9d379800be4ccd pw_allocator: Distinguish between requested, usabl

https://pigweed.googlesource.com/pigweed/pigweed
third_party/pigweed Rolled-Commits: c59bb69e5e17000..55b88ef80fc2403
Roller-URL: https://ci.chromium.org/b/8752383094830980513
GitWatcher: ignore
CQ-Do-Not-Cancel-Tryjobs: true
Change-Id: I558dec14e9c30017d760b3fe34f5244e76015ced
Reviewed-on: https://pigweed-review.googlesource.com/c/pigweed/experimental/+/200170
Bot-Commit: Pigweed Roller <pigweed-roller@pigweed-service-accounts.iam.gserviceaccount.com>
Commit-Queue: Pigweed Roller <pigweed-roller@pigweed-service-accounts.iam.gserviceaccount.com>
diff --git a/third_party/pigweed b/third_party/pigweed
index c59bb69..55b88ef 160000
--- a/third_party/pigweed
+++ b/third_party/pigweed
@@ -1 +1 @@
-Subproject commit c59bb69e5e17000c4120e26c7fc26c309d9f28ce
+Subproject commit 55b88ef80fc2403fc55642ead01b2a71cd0e7448