In case CONFIG_X86_VSMP is not set, limit the number of CPUs to
the number of CPUs of the first board.

Also make CONFIG_X86_VSMP depend on CONFIG_SMP, as there's
little point in having a vsmp machine with a single CPU.
Signed-off-by: NShai Fultheim <shai@scalemp.com>
[ido@wizery.com: rebased, fixed minor coding-style issues]
Signed-off-by: NIdo Yariv <ido@wizery.com>
Signed-off-by: NIngo Molnar <mingo@kernel.org>