[llvm] [RISCV] Only allow up to e64 in vsetvli (PR #92010)

[Palmer Dabbelt via llvm-commits]

palmer-dabbelt wrote:

> Can you add tests to test/MC/RISCV/rvv/invalid.s? I see a test for e2048 in there. I guess we didn't have any tests for e128-e1024.

Done.  Also I fixed up the errors in those tests (I'm no building/testing this locally, I figured some CI would do it for me).

https://github.com/llvm/llvm-project/pull/92010