[ARM,CDE] Cosmetic changes, additonal driver tests

Summary:
This is a follow-up patch addressing post-commit comments in
https://reviews.llvm.org/D74044:

• Add more Clang driver tests (-march=armv8.1m.main and -march=armv8.1m.main+mve.fp)
• Clang-format a chunk in ARMAsmParser.cpp
• Add a missing copyright header to ARMInstrCDE.td

Reviewers: SjoerdMeijer, simon_tatham, dmgreen

Reviewed By: SjoerdMeijer

Subscribers: kristof.beyls, hiraditya, cfe-commits, llvm-commits

Tags: #clang, #llvm

Differential Revision: https://reviews.llvm.org/D74732