roll: third_party/pigweed pw_spi_rp2040: Minor cleanup

* Remove unused LazyInit(): This private method did nothing and was
  never called. We move the comment about spi_init() into docs.rst.

* Remove unused init_status_: This private member was never used.

* Remove unused bits_per_word_: This private member was only written,
  and never read -- except for where it was just set.

* Move constructor initialization list into class definition. This has
  the potential to improve codegen.

Original-Reviewed-on: https://pigweed-review.googlesource.com/c/pigweed/pigweed/+/236233
Original-Revision: 783b29c23dd865fde344501c1b99adba4c956479

Rolled-Repo: https://pigweed.googlesource.com/pigweed/pigweed
Rolled-Commits: 846bb7d3672e94..783b29c23dd865
Roller-URL: https://ci.chromium.org/b/8735814640063749105
GitWatcher: ignore
CQ-Do-Not-Cancel-Tryjobs: true
Change-Id: Ie9e2ee43551f9993ee9a1656a2a53b883afc59ea
Reviewed-on: https://pigweed-review.googlesource.com/c/pigweed/experimental/+/237853
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 846bb7d..783b29c 160000
--- a/third_party/pigweed
+++ b/third_party/pigweed
@@ -1 +1 @@
-Subproject commit 846bb7d3672e94c13451bec81098d3304d8395a9
+Subproject commit 783b29c23dd865fde344501c1b99adba4c956479