usb: ks_bridge: Synchronize disconnect with ongoing IO

Following scenarios possible for interface disconnect racing
with ongoing IO:-

1) Interface disconnect setting interface pointer to NULL and
rx work is executing on other core dereferencing interface
pointer, causing kernel panic. Cancel a work and wait for it
to finish during disconnect.

2) Interface disconnect setting interface pointer to NULL and
tx completion running on other core dereferencing interface
pointer while calling usb_autopm_put_interface_async() API.
Check for USB_DEV_CONNECTED flag(cleared at the time of
disconnect) before dereferencing the interface pointer.

3) Interface unbound and driver is accessing already freed
interface pointer in tx completion or usb device pointer to
re-submit rx urb in rx completion. Add rx and tx urb pending
counters and wait for them to become zero (or timeout) during
disconnect.

(cherry picked from commit b3779d1e3ed31d10c97094256c6d398af8484faa)

Conflicts:

	drivers/usb/misc/ks_bridge.c

CRs-Fixed: 448142
Change-Id: I50341173b94200bcfa60715b4b26b2117fc37c2c
Signed-off-by: Hemant Kumar <hemantk@codeaurora.org>
Signed-off-by: Pavankumar Kondeti <pkondeti@codeaurora.org>