[roll third_party/pigweed] pw_boot_cortex_m: Emit pw_boot_Entry without prologue

As the startup function, pw_boot_Entry must not have a stack frame,
since its jobs include setting the stack pointer and limit.

Original-Bug: b/339107121
Original-Reviewed-on: https://pigweed-review.googlesource.com/c/pigweed/pigweed/+/208931
Lint: Lint 🤖 <android-build-ayeaye@system.gserviceaccount.com>

https://pigweed.googlesource.com/pigweed/pigweed
third_party/pigweed Rolled-Commits: d533f317b8719a8..47018e2757e4c2c
Roller-URL: https://ci.chromium.org/b/8748360530825253249
GitWatcher: ignore
CQ-Do-Not-Cancel-Tryjobs: true
Change-Id: I0fe6fae77247dd4097769756374035583a80a9dd
Reviewed-on: https://pigweed-review.googlesource.com/c/pigweed/examples/+/209084
Commit-Queue: Pigweed Roller <pigweed-roller@pigweed-service-accounts.iam.gserviceaccount.com>
Bot-Commit: Pigweed Roller <pigweed-roller@pigweed-service-accounts.iam.gserviceaccount.com>
Lint: Lint 🤖 <android-build-ayeaye@system.gserviceaccount.com>
diff --git a/third_party/pigweed b/third_party/pigweed
index d533f31..47018e2 160000
--- a/third_party/pigweed
+++ b/third_party/pigweed
@@ -1 +1 @@
-Subproject commit d533f317b8719a8e1fbb8b86b78e7227dd59783d
+Subproject commit 47018e2757e4c2c6d21c371f074bd862897b8843