gnu: linux-libre@4.9: Update to 4.9.231.

* gnu/packages/linux.scm (linux-libre-4.9-version): Update to 4.9.231.
(linux-libre-4.9-pristine-source): Update hash.
(linux-libre-4.9-source): Remove %linux-libre-fix-atheros-9271-patch.
(deblob-scripts-4.9): Update to 4.9.231.