Fix incorrect parsing of UVC interface descriptor

Every USB device that has CS_INTERFACE descriptor was incorrectly
assumed to be an UAC device, without checking the device class.
This led to incorrect parsing of UVC devices, which also have
CS_INTERFACE type descriptors. For some devices the parsing worked
by coincidence, for others it lead to incorrect device data (wrong
vid, pid, etc).

This change parses every CS_INTERFACE descriptor that does not belong
to an UAC device as type 'Unknown'.

Test: Connect a UVC camera, observe logcat.  Before this change, there
were lots of parsing errors in logcat, now the device is added cleanly.

Bug: 124374863
Change-Id: Ic076438625a733cffa9ae51ba803e353fd064ceb
Signed-off-by: Kamen Kirov <knk@pupil-labs.com>