usb: gadget: f_uvc: Fix incorrect wBytesPerInterval

Host fetches no more than wBytesPerInterval data for
every interval in super speed mode.
Since this is being incorrectly calculated function
driver ends up queueing more data than the host
fetches in one interval resulting in MISSED ISOCs
and data loss.
Fix this by using the correct maxburst value to
calcualte the wBytesPerInterval.

Change-Id: I8e4640e6c0f8bc5285e97a0184b7491f6a369146
Signed-off-by: Sriharsha Allenki <sallenki@codeaurora.org>