net: core: dev: Free skb's in dev_cpu_callback

We have been coming across a couple of scenarios where the device
is freed and the corresponding packets which were already queued
up the stack encounter crashes when they find that contents of
skb->dev are no longer valid.

Specifically, we have observed an instance where a cpu hotplug
occurs along with the network driver module unloading. When the
packets are being queued up the stack using netif_rx_ni from
dev_cpu_callback, get_rps_cpus crashes as it encounters invalid
data at skb->dev since it would have been freed.

Since there is no complete fix for this scenario, we try to avoid
this issue by freeing all packets in dev_cpu_callback.

CRs-fixed: 812382
Change-Id: I92846f68f6512444a62cc53a951f3638f08fe2ee
Signed-off-by: Subash Abhinov Kasiviswanathan <subashab@codeaurora.org>