x86: trim ACPI sleep stack buffer

x86_64 SMP suspend to RAM uses a 10k temporary stack for saving the
kernel state, but only 4k of it is used. Shrink it to 4k.
Signed-off-by: Matt Mackall <mpm@selenic.com>
Signed-off-by: Len Brown <len.brown@intel.com>

arch/x86/kernel/acpi/sleep.c

@@ -21,7 +21,7 @@ unsigned long acpi_realmode_flags;
 static unsigned long acpi_realmode;
 
 #if defined(CONFIG_SMP) && defined(CONFIG_64BIT)
-static char temp_stack[10240];
+static char temp_stack[4096];
 #endif
 
 /**