x86/local_apic.c: remove direct SCHED_ULE use

Move the code to decide on the timer accounting into the scheduler hook.
Since there were no inclusion of opt_sched.h, it is probably done
unconditionally anyway.

Reviewed by: olce
Tested by: pho
Sponsored by: The FreeBSD Foundation
MFC after: 1 week
Differential revision: https://reviews.freebsd.org/D54831