gallivm: add InstSimplify pass

This is the recommended replacement for the removed ConstantPropagation
pass, and llvm now added c binding for it.

Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/6585>

src/gallium/auxiliary/gallivm/lp_bld_init.c

@@ -171,6 +171,8 @@ create_pass_manager(struct gallivm_state *gallivm)
       LLVMAddPromoteMemoryToRegisterPass(gallivm->passmgr);
 #if LLVM_VERSION_MAJOR <= 11
       LLVMAddConstantPropagationPass(gallivm->passmgr);
+#else
+      LLVMAddInstructionSimplifyPass(gallivm->passmgr);
 #endif
       LLVMAddInstructionCombiningPass(gallivm->passmgr);
       LLVMAddGVNPass(gallivm->passmgr);