usb: gadget: Fix race condition in connect/disconnect

This commit fixes race condition in fast connect/disconnect
of USB cable. This race condition can also be reproduced in
USB composition change. Thus this commit also adds support
for USB composition change for BAMtoBAM compositions.

CRs-fixed: 463705
Change-Id: I21abaff6a64bb405ce2d698605aff8e0050ef8d6
Signed-off-by: Anna Perel <aperel@codeaurora.org>
Signed-off-by: Bar Weiner <bweiner@codeaurora.org>