kobj: Avoid initializing pointer from boolean value

[zlei]

Summary

Prior to change 477c594d9063, the struct kobj_class has six members but
the DEFINE_CLASS_[0..3] only initialize the first four of them. The
change 477c594d9063 intends to initialize the two new members but
actually acts on the wrong ones.

error: initialization of pointer of type 'kobj_ops_t' (aka 'struct kobj_ops *') to null from a
      constant boolean expression [-Werror,-Wbool-conversion]

Fix by initializing the two new members implicitly.

Fixes: 477c594d9063 kobj: allow multiple inheritance with per-class softc
Reported by: clang (-std=gnu23 -Wbool-conversion)
MFC with: 477c594d9063

[mmel]

Oh, it was a leftover from an earlier version of the struct kobj layout that I forgot to remove. Thanks for fix.

[kib]

Perhaps properly fixing it would change to use designated initializers, as a follow-up.

[zlei]

In D61173#1402811, @kib wrote:

Perhaps properly fixing it would change to use designated initializers, as a follow-up.

I have a WIP for that. Will post when ready.