cxgb4: collect hardware dump in second kernel

Register callback to collect hardware/firmware dumps in second kernel
before hardware/firmware is initialized. The dumps for each device
will be available as elf notes in /proc/vmcore in second kernel.

Signed-off-by: Rahul Lakkireddy <rahul.lakkireddy@chelsio.com>
Signed-off-by: Ganesh Goudar <ganeshgr@chelsio.com>
Signed-off-by: David S. Miller <davem@davemloft.net>