ArmPkg: SpellCheck: Update valid acronyms in ExtendedWords

ArmPkg: SpellCheck: Update valid acronyms in ExtendedWords

REF: https://bugzilla.tianocore.org/show_bug.cgi?id=3445

Spellcheck was not covering all specified files due to CSpell v5 and
Node v10 incompatibility of current CI pipeline configuration.

This change updates ExtendedWords for ArmPkg with valid acronyms to avoid
potential spell errors.

Cc: Laszlo Ersek <lersek@redhat.com>
Cc: Ard Biesheuvel <ardb+tianocore@kernel.org>
Cc: Leif Lindholm <leif@nuviainc.com>
Cc: Sami Mujawar <sami.mujawar@arm.com>
Signed-off-by: Sean Brogan <sean.brogan@microsoft.com>
Signed-off-by: Kun Qin <kuqin12@gmail.com>
Reviewed-by: Ard Biesheuvel <ardb@kernel.org>