Guard vDSO code with CONFIG_VDSO, no need to even build it
on archs which do not support vDSO handling.
Signed-off-by: Cyrill Gorcunov <gorcunov@openvz.org>
Acked-by: Alexander Kartashov <alekskartashov@parallels.com>
Signed-off-by: Pavel Emelyanov <xemul@parallels.com>