[llvm] [llvm-objdump] Support --mcpu=help/--mattr=help without -d (PR #165661)

[James Henderson via llvm-commits]

jh7370 wrote:

> > Do you have commit access yet?
> 
> Probably not, as I haven't submitted the request yet.

Okay, would you like me to merge this?

https://github.com/llvm/llvm-project/pull/165661