HID: add hid_hw_open/close/power() handlers

Instead of exposing the guts of hid->ll_driver relationship to HID
sub-drivers provide these helpers to encapsulate the details.

Signed-off-by: Dmitry Torokhov <dtor@mail.ru>
Signed-off-by: Jiri Kosina <jkosina@suse.cz>
diff --git a/drivers/hid/hid-input.c b/drivers/hid/hid-input.c
index 834ef47..b718f71 100644
--- a/drivers/hid/hid-input.c
+++ b/drivers/hid/hid-input.c
@@ -772,14 +772,14 @@
 {
 	struct hid_device *hid = input_get_drvdata(dev);
 
-	return hid->ll_driver->open(hid);
+	return hid_hw_open(hid);
 }
 
 static void hidinput_close(struct input_dev *dev)
 {
 	struct hid_device *hid = input_get_drvdata(dev);
 
-	hid->ll_driver->close(hid);
+	hid_hw_close(hid);
 }
 
 /*