[roll third_party/pigweed] freertos: Add bazel support for xtensa port

Split port specific headers into own target since the definitions are
used in FreeRTOSConfig.h. This avoids a circular dependency.

Original-Reviewed-on: https://pigweed-review.googlesource.com/c/pigweed/pigweed/+/152171

https://pigweed.googlesource.com/pigweed/pigweed
third_party/pigweed Rolled-Commits: 1da5c3aac6aa3cb..ead759cc68e4f35
Roller-URL: https://ci.chromium.org/b/8778091646197408993
GitWatcher: ignore
CQ-Do-Not-Cancel-Tryjobs: true
Change-Id: I61fe8c5a0ed282de4ab4413a2f723ca41e4a2391
Reviewed-on: https://pigweed-review.googlesource.com/c/pigweed/experimental/+/152267
Bot-Commit: 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 1da5c3a..ead759c 160000
--- a/third_party/pigweed
+++ b/third_party/pigweed
@@ -1 +1 @@
-Subproject commit 1da5c3aac6aa3cbaad07a0b1ac97210c3e846f13
+Subproject commit ead759cc68e4f35b63e2e2f202c69be82c9157b4