IB/umad: Convert *cdev to cdev in struct ib_umad_port

Instead of storing pointers to cdev and sm_cdev, embed the full
structures instead.

This change allows us to use the container_of() macro in ib_umad_open()
and ib_umad_sm_open() in a future patch.

This change increases the size of struct ib_umad_port to 320 bytes
from 128.

Signed-off-by: Alex Chiang <achiang@hp.com>
Signed-off-by: Roland Dreier <rolandd@cisco.com>