Split to each individual driver for POD, PODHD, TonePort and Variax
with a core LINE6 helper module.  The new modules follow the standard
ALSA naming rule with snd prefix: snd-usb-pod, snd-usb-podhd,
snd-usb-toneport and snd-usb-variax, together with the corresponding
CONFIG_SND_USB_* Kconfig items.
Tested-by: NChris Rorvick <chris@rorvick.com>
Signed-off-by: NTakashi Iwai <tiwai@suse.de>