[roll pigweed] pw_boot_cortex_m: Add comment to linker file

Adds a comment to basic_cortex_m.ld that was previously in a CL
description.

Original-Reviewed-on: https://pigweed-review.googlesource.com/c/pigweed/pigweed/+/107174

https://pigweed.googlesource.com/pigweed/pigweed
pigweed Rolled-Commits: a3538880dd836b4..dd36f09cae0fc11
Roller-URL: https://ci.chromium.org/b/8805463705665201793
CQ-Do-Not-Cancel-Tryjobs: true
Change-Id: I9e7e1bb87f7ef22dfe5325d2ace7e62e8e046a21
Reviewed-on: https://pigweed-review.googlesource.com/c/pigweed/zephyr-integration/+/107392
Commit-Queue: Pigweed Integration Roller <pigweed-integration-roller@pigweed.google.com.iam.gserviceaccount.com>
Bot-Commit: Pigweed Integration Roller <pigweed-integration-roller@pigweed.google.com.iam.gserviceaccount.com>
diff --git a/pigweed b/pigweed
index a353888..dd36f09 160000
--- a/pigweed
+++ b/pigweed
@@ -1 +1 @@
-Subproject commit a3538880dd836b455d5878ba4e0606637478abde
+Subproject commit dd36f09cae0fc11627bedca6e2861a7cf10b4b31