MAINTAINERS: add Tom as clang reviewer

I have been helping with build breaks and other clang things and would
like to help with the reviews.

Link: https://lkml.kernel.org/r/20220407175715.3378998-1-trix@redhat.com
Signed-off-by: Tom Rix <trix@redhat.com>
Acked-by: Nathan Chancellor <nathan@kernel.org>
Acked-by: Nick Desaulniers <ndesaulniers@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

Author: Tom Rix

MAINTAINERS

@@ -4791,6 +4791,7 @@ F:	.clang-format
 CLANG/LLVM BUILD SUPPORT
 M:	Nathan Chancellor <nathan@kernel.org>
 M:	Nick Desaulniers <ndesaulniers@google.com>
+R:	Tom Rix <trix@redhat.com>
 L:	llvm@lists.linux.dev
 S:	Supported
 W:	https://clangbuiltlinux.github.io/