[clang] [Clang][Sema] Fix missing warning when comparing mismatched enums in … (PR #81418)

[Nathan Chancellor via cfe-commits]

nathanchance wrote:

For what it's worth, this change adds several instances of `-Wenum-enum-conversion` for the Linux kernel: https://github.com/ClangBuiltLinux/linux/issues/2002. I assume this is intentional given the nature of the change as a whole but neither the tests nor the release notes seem to really reflect that. In case it is a bug that this change affected that, consider this a report :)

https://github.com/llvm/llvm-project/pull/81418