[roll third_party/pigweed] pw_digital_io_linux: Move OwnedFd to its own header file

Original-Reviewed-on: https://pigweed-review.googlesource.com/c/pigweed/pigweed/+/207831
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https://pigweed.googlesource.com/pigweed/pigweed
third_party/pigweed Rolled-Commits: 6fb2433c30e6733..5bda8d1632020bd
Roller-URL: https://ci.chromium.org/b/8749107729980713729
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Change-Id: Ie2ebc90434ae2cd72919b8fccdc0fdb05b7d2bae
Reviewed-on: https://pigweed-review.googlesource.com/c/pigweed/experimental/+/207639
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diff --git a/third_party/pigweed b/third_party/pigweed
index 6fb2433..5bda8d1 160000
--- a/third_party/pigweed
+++ b/third_party/pigweed
@@ -1 +1 @@
-Subproject commit 6fb2433c30e6733754df8c5ab1d81fd568325977
+Subproject commit 5bda8d1632020bdcd2839ddeefdc796319499152