msm: ipa: tethering bridge: add support for tetherless host

By doing a cleanup on USB cable disconnect, it is possible to connect the
device to different hosts with different link protocols and
aggregation parameters without resetting the device.

Change-Id: I9cee577ebc3313d199125eb0471fe3d60f5b9958
Signed-off-by: Gidon Studinski <gidons@codeaurora.org>