[llvm] [RISCV] Remove RISCVISD opcodes for LGA, LA_TLS_IE, and LA_TLS_GD. (PR #70137)

[Philip Reames via llvm-commits]

https://github.com/preames approved this pull request.

LGTM - No strong preference here either way, so defer to you on preference.

https://github.com/llvm/llvm-project/pull/70137