[ALSA] Repair snd-usb-usx2y for usb 2.6.18

urb->start_frame rolls over beyond MAX_INT now.
This is for stable kernel and stable alsa.

Signed-off-by: Karsten Wiese <annabellesgarden@yahoo.de>
Signed-off-by: Takashi Iwai <tiwai@suse.de>
Signed-off-by: Jaroslav Kysela <perex@suse.cz>