net: qualcomm: rmnet: Fix use after free while sending command ack

When sending an ack to a command packet, the skb is still referenced
after it is sent to the real device. Since the real device could
free the skb, the device pointer would be invalid.
Also, remove an unnecessary variable.

CRs-Fixed: 2233026
Change-Id: I79baf20b52a51041d2d1a4da73a70fb4b320544e
Fixes: ceed73a2 ("drivers: net: ethernet: qualcomm: rmnet: Initial implementation")
Signed-off-by: David S. Miller <davem@davemloft.net>
Git-commit: 3602207ca6582dd359308b7bd2ce08348cc0854e
Git-repo: git://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git


Signed-off-by: Subash Abhinov Kasiviswanathan <subashab@codeaurora.org>