Call pmc_hook() correctly in the ARM64 interrupt handler

pmc_hook() was called only in case of the stray interrupt but should
rather be called on each interrupt. Move in to the arm_cpu_intr()
handler, out of the critical section too.

Reviewed by: br
Obtained from: Semihalf
Sponsored by: Cavium
Differential Revision: https://reviews.freebsd.org/D5161