[INFINIBAND]: Add InfiniBand MAD (management datagram) support

Add support for handling InfiniBand MADs (management datagrams),
including sending and receiving MADs as well as passing MADs on to
local agents.

This is required for an SM (subnet manager) to discover and configure
the host, since the SM's query MADs must be passed to the local SMA
(subnet management agent).  In addition, this support is used by upper
level protocols to send queries to and receive responses from the SM.
Signed-off-by: Roland Dreier <roland@topspin.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/infiniband/core/Makefile

 EXTRA_CFLAGS += -Idrivers/infiniband/include
 
-obj-$(CONFIG_INFINIBAND) +=	ib_core.o
+obj-$(CONFIG_INFINIBAND) +=	ib_core.o ib_mad.o
 
 ib_core-y :=			packer.o ud_header.o verbs.o sysfs.o \
 				device.o fmr_pool.o cache.o
+
+ib_mad-y :=			mad.o smi.o agent.o