tools/kvm_stat: mark private methods as such

tools/kvm_stat: mark private methods as such

BugLink: http://bugs.launchpad.net/bugs/1734130
Helps quite a bit reading the code when it's obvious when a method is
intended for internal use only.

Signed-off-by: Stefan Raspl <raspl@linux.vnet.ibm.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
(cherry picked from commit c0e8c21eae616ed8703c1b4b01046a1578ee875c)
Signed-off-by: Seth Forshee <seth.forshee@canonical.com>
Acked-by: Thadeu Lima de Souza Cascardo <cascardo@canonical.com>
Signed-off-by: Thadeu Lima de Souza Cascardo <cascardo@canonical.com>