x86: fix sleep.c build error

fix:

arch/x86/kernel/acpi/sleep.c: In function ‘acpi_save_state_mem':
arch/x86/kernel/acpi/sleep.c:75: error: ‘stack_start' undeclared (first use in this function)
arch/x86/kernel/acpi/sleep.c:75: error: (Each undeclared identifier is reported
only once
arch/x86/kernel/acpi/sleep.c:75: error: for each function it appears in.)

Signed-off-by: Ingo Molnar <mingo@elte.hu>

1 files changed, 2 insertions, 0 deletions

diff --git a/arch/x86/kernel/acpi/sleep.c b/arch/x86/kernel/acpi/sleep.c
index a81f468ab410..e6a4b564ccaa 100644
--- a/arch/x86/kernel/acpi/sleep.c
+++ b/arch/x86/kernel/acpi/sleep.c
@@ -86,7 +86,9 @@ int acpi_save_state_mem(void)
         saved_magic = 0x12345678;
 #else /* CONFIG_64BIT */
         header->trampoline_segment = setup_trampoline() >> 4;
+#ifdef CONFIG_SMP
         stack_start.sp = temp_stack + 4096;
+#endif
         initial_code = (unsigned long)wakeup_long64;
         saved_magic = 0x123456789abcdef0;
 #endif /* CONFIG_64BIT */