x86/platform/olpc: Fix resume handler build warning

Fix:

  arch/x86/platform/olpc/olpc-xo15-sci.c:199:12: warning: ‘xo15_sci_resume’
  defined but not used [-Wunused-function]
   static int xo15_sci_resume(struct device *dev)
              ^

which I see in randconfig builds here.
Signed-off-by: Borislav Petkov <bp@suse.de>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Link: http://lkml.kernel.org/r/20161126142706.13602-1-bp@alien8.deSigned-off-by: Ingo Molnar <mingo@kernel.org>

arch/x86/platform/olpc/olpc-xo15-sci.c

@@ -196,6 +196,7 @@ static int xo15_sci_remove(struct acpi_device *device)
 	return 0;
 }
 
+#ifdef CONFIG_PM_SLEEP
 static int xo15_sci_resume(struct device *dev)
 {
 	/* Enable all EC events */
@@ -207,6 +208,7 @@ static int xo15_sci_resume(struct device *dev)
 
 	return 0;
 }
+#endif
 
 static SIMPLE_DEV_PM_OPS(xo15_sci_pm, NULL, xo15_sci_resume);