usb: gadget: Ensure no pending works in bam drivers before init works

Due to valid race conditions, it may be possible that there
is a re-connect while there are pending works in the workqueue.
In case of re-connect, there is a reset of the works, and we need to do
this only if there are no pending, otherwise we will get access violation
when kworker will try to fetch the next work.

CRs-Fixed: 680422
Change-Id: Id1538bd57d9dd5df793cdafe2aa8464c1017885c
Signed-off-by: Ido Shayevitz <idos@codeaurora.org>