Fix a number of races during initialization of SR-IOV on ixl:
- Fix cases that were touching ixl_vf instances before they were initialized
- I'm seeing issues where adminq interrupts seemingly are never delivered. I haven't been able to get to root cause so instead make sure that the timer is running while SR-IOV is enabled, which has a safety belt for missed adminq interrupts already.
- Flush register writes that enable/disable interrupts in the SR-IOV code paths.