sound: usb: Handle audio control interface descriptor properly

usb audio qmi driver is incorrectly passing non-zero alternate
interface related class specific buffer to parse the UAC header.
This is causing driver to respond with incorrect bcdADC value.
Fix this issue by reading the cached audio control interface
context which is saved upon driver probe for the first audio
interface. Also differentiate UAC version of header when type
casting the UAC header descriptor.

Change-Id: Ice62887451e91901cb16a6356b64f554b95eacc4
Signed-off-by: Hemant Kumar <hemantk@codeaurora.org>