perf kvm: Make function only used by 'perf kvm' static

No need to have this polluting util.h, it was polluted enough already.

Link: http://lkml.kernel.org/n/tip-wfdidqlwbvi5y0s61kv6z2gn@git.kernel.org


Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>