x86: hypervisor - fix sparse warnings

Impact: fix sparse build warning

Fix the following sparse warnings:

  arch/x86/kernel/cpu/hypervisor.c:37:15: warning: symbol
  'get_hypervisor_tsc_freq' was not declared. Should it be static?
  arch/x86/kernel/cpu/hypervisor.c:53:16: warning: symbol
  'init_hypervisor' was not declared. Should it be static?

Signed-off-by: Hannes Eder <hannes@hanneseder.net>
Cc: "Alok N Kataria" <akataria@vmware.com>
Cc: "Dan Hecht" <dhecht@vmware.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>