[llvm] [Mips] Add set directive support for EVA instructions (PR #225888)

[Anand Mistry via llvm-commits]

akmistry-msft wrote:

> From binutils:
> 
> ```
> #define TLBINV ASE_EVA
> 
> {"tlbinv",  "", 0x42000003, 0xffffffff, INSN_TLB, 0, I37, TLBINV, 0 },
> {"tlbinvf", "", 0x42000004, 0xffffffff, INSN_TLB, 0, I37, TLBINV, 0 },
> ```
> 
> It has I37 and EVA with or condition, that means tlbinv should be enabled for MIPS32/64 R6, or ealier release with EVA ASE.
> 
> `.set eva` change LGTM, if it's too much for you to fix the instruction availbility I can do a follow up PR.
> 
> Thanks

I'm not too familar with the code to be able to do this.

Also, rebased to re-trigger buildkite.

https://github.com/llvm/llvm-project/pull/225888