tools: kvm_stat: Powerpc related fixes

kvm_stat script is failing to execute on powerpc :
 # ./kvm_stat
Traceback (most recent call last):
  File "./kvm_stat", line 825, in <module>
    main()
  File "./kvm_stat", line 813, in main
    providers = get_providers(options)
  File "./kvm_stat", line 778, in get_providers
    providers.append(TracepointProvider())
  File "./kvm_stat", line 416, in __init__
    self.filters = get_filters()
  File "./kvm_stat", line 315, in get_filters
    if ARCH.exit_reasons:
AttributeError: 'ArchPPC' object has no attribute 'exit_reasons'

This is because, its trying to access a non-defined attribute.

Also, the IOCTL number of RESET is incorrect for powerpc. The correct
number has been added.

Signed-off-by: Hemant Kumar <hemant@linux.vnet.ibm.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>