[Clang] Add 'Joseph Huber' as offloading driver maintainer (#133296)

Summary:
I am probably the person most familiar with the offloading pipeline in
clang at this point.
diff --git a/clang/Maintainers.rst b/clang/Maintainers.rst
index ef41628..dfe86a0 100644
--- a/clang/Maintainers.rst
+++ b/clang/Maintainers.rst
@@ -159,6 +159,11 @@
 | Brad Smith
 | brad\@comstyle.com (email), brad (Phabricator), brad0 (GitHub)
 
+Offloading driver
+~~~~~~~~~~~~~~~~~
+| Joseph Huber
+| joseph.huber\@amd.com (email), jhuber6 (GitHub)
+
 
 Driver parts not covered by someone else
 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~