draw/orcjit: supply stub function for tcs coro

This fixes a crash with shader cache enabled:
JIT session error: Unexpected definitions in module : [ draw_llvm_tcs_coro_variant ]
Failed to materialize symbols: { (draw_llvm_tcs_variant0_7, { draw_llvm_tcs_variant }) }

Fixes: bb0efdd4d896 ("llvmpipe: add shader cache support for ORCJIT implementation")
Reviewed-by: Icenowy Zheng <uwu@icenowy.me>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/30335>
(cherry picked from commit fcf9e33ec0e51ee8f22463b388a3bcefd3b5f572)