usb: gadget: u_audio: EP-OUT bInterval in fback frequency

usb: gadget: u_audio: EP-OUT bInterval in fback frequency

The patch increases the bitshift in feedback frequency
calculation with EP-OUT bInterval value.

Tests have revealed that Win10 and OSX UAC2 drivers require
the feedback frequency to be based on the actual packet
interval instead of on the USB2 microframe. Otherwise they
ignore the feedback value. Linux snd-usb-audio driver
detects the applied bitshift automatically.

Tested-by: Henrik Enquist <henrik.enquist@gmail.com>
Signed-off-by: Pavel Hofman <pavel.hofman@ivitera.com>
Cc: stable <stable@vger.kernel.org>
Link: https://lore.kernel.org/r/20210906130822.12256-1-pavel.hofman@ivitera.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>