x86: fix build breakage when PCI is define and PARAVIRT is not

- Fix the the build breakage when PARAVIRT is defined
  but PCI is not
  This fixes problem reported at:
	http://marc.info/?l=linux-kernel&m=120525966600698&w=2
- Make is_vsmp_box() available even when PARAVIRT is not defined.
  This is needed to determine if tsc's are reliable as a time source
  even when PARAVIRT is not defined.
- split vsmp_init to use is_vsmp_box() and set_vsmp_pv_ops()
  set_vsmp_pv_ops will do nothing if PCI is not enabled in the config.

Signed-off-by: Ravikiran Thirumalai <kiran@scalex86.org>
Signed-off-by: Ingo Molnar <mingo@elte.hu>