acer-wmi: Hide acer_{suspend,resume} for !CONFIG_PM_SLEEP

Encapsulate acer_suspend() and acer_resume with #ifdef CONFIG_PM_SLEEP
to get rid of the following warnings:

  ../acer-wmi.c:2046:12: warning: ‘acer_suspend’ defined but not used [-Wunused-function]
  ../acer-wmi.c:2068:12: warning: ‘acer_resume’ defined but not used [-Wunused-function]
Signed-off-by: Mathias Krause <minipli@googlemail.com>
Cc: "Lee, Chun-Yi" <jlee@suse.com>
Signed-off-by: Matthew Garrett <matthew.garrett@nebula.com>

drivers/platform/x86/acer-wmi.c

@@ -2043,6 +2043,7 @@ static int acer_platform_remove(struct platform_device *device)
 	return 0;
 }
 
+#ifdef CONFIG_PM_SLEEP
 static int acer_suspend(struct device *dev)
 {
 	u32 value;
@@ -2083,6 +2084,10 @@ static int acer_resume(struct device *dev)
 
 	return 0;
 }
+#else
+#define acer_suspend	NULL
+#define acer_resume	NULL
+#endif
 
 static SIMPLE_DEV_PM_OPS(acer_pm, acer_suspend, acer_resume);