roll: third_party/pigweed pw_sync: Support yield on riscv64

Add a `PW_SYNC_YIELD_CORE_FOR_SMT` implementation for riscv targets.

Original-Bug: b/380453709
Test: Manually on downstream project

Original-Reviewed-on: https://pigweed-review.googlesource.com/c/pigweed/pigweed/+/279533
Tests-Not-Needed: Eric Rahm <erahm@google.com>
Original-Revision: e078345062efc9717a9bda19b5c9afac82df2e0a

Rolled-Repo: https://pigweed.googlesource.com/pigweed/pigweed
Rolled-Commits: b4a6f35859591e..e078345062efc9
Roll-Count: 1
Roller-URL: https://cr-buildbucket.appspot.com/build/8719190208729150993
GitWatcher: ignore
CQ-Do-Not-Cancel-Tryjobs: true
Change-Id: I8c2f25203496558534af44ffa365512650f48d1e
Reviewed-on: https://pigweed-review.googlesource.com/c/pigweed/examples/+/279934
Lint: Lint 🤖 <android-build-ayeaye@system.gserviceaccount.com>
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 b4a6f35..e078345 160000
--- a/third_party/pigweed
+++ b/third_party/pigweed
@@ -1 +1 @@
-Subproject commit b4a6f35859591eee9e89ce429f811495d2053892
+Subproject commit e078345062efc9717a9bda19b5c9afac82df2e0a