Remove "__tsan_func_entry()"/"__tsan_func_exit()" if nothing was instrumented in the function.

```llvm
define dso_local void @func() #0 !dbg !22 {
entry:
  %0 = call ptr @llvm.returnaddress(i32 0), !dbg !25
  call void @__tsan_func_entry(ptr %0), !dbg !25

  %1 = load i32, ptr @a, align 4, !dbg !25
  %inc = add nsw i32 %1, 1, !dbg !25
  store i32 %inc, ptr @a, align 4, !dbg !25

  call void @__tsan_func_exit(), !dbg !27
  ret void, !dbg !27
}
```