USB: mdm_bridge: Fix a possible freed memory access

When tethered rmnet/dun interface probe is failed, the bridge channel
platform device is removed in error path.  The gadget driver schedule
a work to open the bridge channel in probe.  Cancel this work in remove
before closing the channel.

Cancel any pending work while closing the bridge.  Otherwise there is
a possibility of rx work running in parallel with probe error path.  If
this happens, rx work access already freed memory.

CRs-Fixed: 442119
(cherry picked from commit 50f3815166483c654ebb325c49e50af4e31547da)

Change-Id: I78c2ee04cfd083248127cfd6b9f07994087729ca
Signed-off-by: Pavankumar Kondeti <pkondeti@codeaurora.org>