net: rmnet_data: Unset logical end points in bridge mode

We clean up the logical end points only for the un-registering device
in bridge mode. However, the other physical end point's local end
point still points to the the un-registered device.

This may lead up to a crash if one of the physical devices in bridge
mode is un-registered. Fix this by unsetting the local endpoint.

It is still possible that packets in a different context across cores
might try to access this data. This usually manifests as packets
requesting a very large headroom. Handle this by dropping these stale
skb's.

CRs-Fixed: 1098513
Change-Id: I1ba4d877a6ed3eca66946fe056938f0927bcd9a5
Signed-off-by: Subash Abhinov Kasiviswanathan <subashab@codeaurora.org>
Signed-off-by: Ashwanth Goli <ashwanth@codeaurora.org>