If the system supports hypervisor based statistics, allow them to
be fetched, enabled, and disabled via sysfs.
Enable and disable via the boolean:
/sys/devices/systems/cpu/cpuN/mmustat_enable
Statistic values are provided under:
/sys/devices/systems/cpu/cpuN/mmu_status/
Signed-off-by: David S. Miller <davem@davemloft.net>