Add a driver that provides a character special device for each
InfiniBand port.  This device allows userspace to send and receive
MADs via write() and read() (with some control operations implemented
as ioctls).

All operations are 32/64 clean and have been tested with 32-bit
userspace running on a ppc64 kernel.
Signed-off-by: Roland Dreier <roland@topspin.com>
Signed-off-by: David S. Miller <davem@davemloft.net>