[roll third_party/pigweed] pw_persistent_ram: add Persistent size report

Original-Reviewed-on: https://pigweed-review.googlesource.com/c/pigweed/pigweed/+/38581

third_party/pigweed Rolled-Commits: 32dc5c52cad8c3f..ac6a6acfb74e760
Roller-URL: https://ci.chromium.org/b/8852318094617796192
Cq-Cl-Tag: roller-builder:pigweed-experimental-roller
Cq-Cl-Tag: roller-bid:8852318094617796192
CQ-Do-Not-Cancel-Tryjobs: true
Change-Id: I33d76ff27b2ebf68e678446511b4e9a5ad822d58
Reviewed-on: https://pigweed-review.googlesource.com/c/pigweed/experimental/+/38660
Reviewed-by: Pigweed Integration Roller <pigweed-integration-roller@pigweed.google.com.iam.gserviceaccount.com>
Commit-Queue: Pigweed Integration Roller <pigweed-integration-roller@pigweed.google.com.iam.gserviceaccount.com>
diff --git a/third_party/pigweed b/third_party/pigweed
index 32dc5c5..ac6a6ac 160000
--- a/third_party/pigweed
+++ b/third_party/pigweed
@@ -1 +1 @@
-Subproject commit 32dc5c52cad8c3ffd2ba3c7a4cdf1109b7e5e5ff
+Subproject commit ac6a6acfb74e7604b6dac322b8eb14a9cefd553d