infiniband: make cm_device use a struct device and not a kobject.

This object really should be a struct device, or at least contain a
pointer to a struct device, as it is trying to create a separate device
tree outside of the main device tree.  This patch fixes this problem.

It is needed for the class core rework that is being done in the driver
core.

Cc: Kay Sievers <kay.sievers@vrfy.org>
Cc: Roland Dreier <rolandd@cisco.com>
Cc: Sean Hefty <sean.hefty@intel.com>
Cc: Hal Rosenstock <hal.rosenstock@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>