[clang] [Driver] Support -mcmodel= for LoongArch (PR #72514)

[Lu Weining via cfe-commits]

SixWeining wrote:

> > And AFAIK, gcc side doesn't plan to implement the "large" code model.
> 
> Why did we distinguish "large" and "extreme" in the first place? If we don't need a different "large" code model then I guess we should make it an alias of "extreme" for GCC too.

@ChenghuaXu @chenglulu326 What do you think?

https://github.com/llvm/llvm-project/pull/72514