arm64 gicv3_its: enable all ITS blocks for a CPU

We now support multiple ITS blocks raising interrupts to a CPU.
Add all available CPUs to the ITS when no NUMA information is
available.

This reverts the check added in r340602, at that tim we did not
suppport multiple ITS blocks for a CPU.

Differential Revision: https://reviews.freebsd.org/D20417