Move some cpu_xxxx() function to cpus.c

This moves the following functions from qemu-timer.c to cpus.c to match
upstream:

  cpu_get_ticks
  cpu_get_clock
  cpu_enable_ticks
  cpu_disable_ticks
  timer_save
  timer_load

+ Move declarations from include/qemu/timer.h to include/sysemu/sysemu.h
+ Remove obsolete declarations from include/qemu/timer.h

Change-Id: I83c84cf4c6fb83cbda6a501969e05fbffb4afd4f
4 files changed