On MP kernels, invoke SPINLOCK_SPIN_HOOK in mtx_enter() when it spins.
On MP kernels, invoke SPINLOCK_SPIN_HOOK in mtx_enter() when it spins.

orumin/openbsd-efivars,orumin/openbsd-efivars,orumin/openbsd-efivars,orumin/openbsd-efivars