rmnet devices cannot have a mux id of 255. This is validated when
assigning the mux id to the rmnet devices. As a result, checking for
mux id 255 does not apply in egress path.
Signed-off-by: NSubash Abhinov Kasiviswanathan <subashab@codeaurora.org>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>