ALSA: usb-audio: Check endpoint numbers at parsing Scarlett2 mixer interfaces

In the Linux kernel, the following vulnerability has been resolved: ALSA: usb-audio: Check endpoint numbers at parsing Scarlett2 mixer interfaces The Scarlett2 mixer quirk in USB-audio driver may hit a NULL dereference when a malformed USB descriptor is passed, since it assumes the presence of an endpoint in the parsed interface in scarlett2_find_fc_interface(), as reported by fuzzer. For avoiding the NULL dereference, just add the sanity check of bNumEndpoints and skip the invalid interface.