ANDROID: trusty: Call kthread_set_per_cpu

Call the new kthread_set_per_cpu api to make sure the kthreads we
created with kthread_create_on_cpu stay on the required cpu.

Bug: 266595872
Bug: 274202992
Change-Id: I741191329bf53f78d2613164a8390a1a14515b71
Signed-off-by: Arve Hjønnevåg <arve@android.com>