Fix a possible hang which apparently occurs during a warm boot (cold boot
does not display the symptom). Evidently the ifpi2 controller needs to be
massaged more than it was.

Note that this does not close the PR since it was filed against 4.9.

MFC: 5 days
PR: kern/68756
Submitted by: Ari Suutari <ari.suutari@syncrontech.com>