[PATCH] x86_64: fix build without HOTPLUG_CPU

cpu_vsyscall_notifier() is defined only when CONFIG_HOTPLUG_CPU is
defined.

Signed-off-by: Jiri Kosina

--- 

 arch/x86_64/kernel/vsyscall.c |    2 ++
 1 files changed, 2 insertions(+), 0 deletions(-)

diff --git a/arch/x86_64/kernel/vsyscall.c b/arch/x86_64/kernel/vsyscall.c
index 3416462..e93ffcf 100644
--- a/arch/x86_64/kernel/vsyscall.c
+++ b/arch/x86_64/kernel/vsyscall.c
@@ -307,7 +307,9 @@ #ifdef CONFIG_SYSCTL
 	register_sysctl_table(kernel_root_table2, 0);
 #endif
 	on_each_cpu(cpu_vsyscall_init, NULL, 0, 1);
+#ifdef CONFIG_HOTPLUG_CPU
 	hotcpu_notifier(cpu_vsyscall_notifier, 0);
+#endif
 	return 0;
 }