ACPI: check a return value correctly in acpi_power_get_context()

We should check *resource != NULL rather than resource != NULL, which will be
always true.
Signed-off-by: NLi Zefan <lizf@cn.fujitsu.com>
Acked-by: NZhao Yakui <yakui.zhao@intel.com>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLen Brown <len.brown@intel.com>

drivers/acpi/power.c

@@ -121,7 +121,7 @@ acpi_power_get_context(acpi_handle handle,
 	}
 
 	*resource = acpi_driver_data(device);
-	if (!resource)
+	if (!*resource)
 		return -ENODEV;
 
 	return 0;