ALSA: line6: Remove superfluous NULL checks in each driver

The interface and driver objects are always set when callbacks are
called.  Drop such superfluous NULL checks in init and disconnect
calls of each driver.

Tested-by: Chris Rorvick <chris@rorvick.com>
Signed-off-by: Takashi Iwai <tiwai@suse.de>

sound/usb/line6/variax.c

@@ -214,12 +214,7 @@ static void line6_variax_disconnect(struct usb_interface *interface)
 {
 	struct usb_line6_variax *variax;
 
-	if (!interface)
-		return;
-
 	variax = usb_get_intfdata(interface);
-	if (!variax)
-		return;
 
 	del_timer(&variax->startup_timer1);
 	del_timer(&variax->startup_timer2);
@@ -244,9 +239,6 @@ static int variax_init(struct usb_interface *interface,
 	init_timer(&variax->startup_timer2);
 	INIT_WORK(&variax->startup_work, variax_startup6);
 
-	if ((interface == NULL) || (variax == NULL))
-		return -ENODEV;
-
 	/* initialize USB buffers: */
 	variax->buffer_activate = kmemdup(variax_activate,
 					  sizeof(variax_activate), GFP_KERNEL);