Integrate LLVM at bfab8085af878dbcafaf5dfac4e34dc17a20971c (#21747)

Reverts b4c31dc98dfc929728904cd96f0f4cf812c4d5b5 because it needs
changes to allow vector.from_elements lowering
diff --git a/third_party/llvm-project b/third_party/llvm-project
index c65c0e8..c307f91 160000
--- a/third_party/llvm-project
+++ b/third_party/llvm-project
@@ -1 +1 @@
-Subproject commit c65c0e87fc73940bc18e9cc0a32aadd381e292a3
+Subproject commit c307f91d1df9cb108dcae26760aa5c8d95ee5747