Update this according to USB Audio Class 1.0 spec. This fixes the Windows 7
detection issue.

Cc: Rafael Brune <mail@rbrune.de>
Signed-off-by: Xuebing Wang <xbing6@gmail.com>
Signed-off-by: Fabio Estevam <festevam@gmail.com>
Signed-off-by: Peter Chen <peter.chen@freescale.com>
(Fixed some code style issues)
Tested-by: Peter Chen <peter.chen@freescale.com>
Signed-off-by: Felipe Balbi <balbi@ti.com>