UCT/IB: Support device speed change event from rdma-core and driver

UCX receives IBV_EVENT_PORT_SPEED_CHANGE event and adjust the speed accordingly,
but rdma-core actually provides IBV_EVENT_DEVICE_SPEED_CHANGE event carrying port number
zero, which cannot trigger the speed adjust logic of UCX.

This commit adds support for IBV_EVENT_DEVICE_SPEED_CHANGE and keeps compatible
with IBV_EVENT_PORT_SPEED_CHANGE.

Signed-off-by: Zhenlong Ma <mazhenlong321@gmail.com>