The current backend uses direct field access to the backing field
instead of calling the companion object accessor, which calls
an accessibility bridge, which then gets the field for code such as:
```
class A {
companion object {
val s: String = "OK"
}
// f uses direct access to the A.s backing field.
fun f() = s
}
```
This change does the same for the IR backend.
Steven Schäfer