net: qualcomm: rmnet: Always assign rmnet dev in deaggregation path

The rmnet device needs to assigned for all packets in the
deaggregation path based on the mux id, so the check is not needed.

Signed-off-by: Subash Abhinov Kasiviswanathan <subashab@codeaurora.org>
Signed-off-by: David S. Miller <davem@davemloft.net>