NTB: client event cleanup

Provide a better event interface between the client and transport

Signed-off-by: Jon Mason <jon.mason@intel.com>

diff --cc drivers/net/ntb_netdev.c
Simple merge

diff --cc drivers/ntb/ntb_hw.h
Simple merge

diff --cc drivers/ntb/ntb_transport.c
Simple merge

diff --cc include/linux/ntb.h
Simple merge