MFC 265913, 265914:

MFC 265913, 265914:

  Interrupts need to be disabled on entry to cpu_sleep() for ARM.  Given
  that and the need to be in a critical section when switching to idleclock
  mode for event timers, use spinlock_enter()/exit() to achieve both needs.

  Clean up some style nits.

git-svn-id: svn://svn.freebsd.org/base/stable/10@266388 ccf9f872-aa2e-dd11-9fc8-001c23d0bc1f