net/smc: adapt SMC remote DELETE_RKEY processing to use the LLC flow

Use the LLC flow framework for the processing of DELETE_RKEY messages
that were received from the peer.

Signed-off-by: Karsten Graul <kgraul@linux.ibm.com>
Reviewed-by: Ursula Braun <ubraun@linux.ibm.com>
Signed-off-by: David S. Miller <davem@davemloft.net>