RDMA/nes: Generate IB_EVENT_PORT_ERR/PORT_ACTIVE events

Depending on link state change, IB_EVENT_PORT_ERR or
IB_EVENT_PORT_ACTIVE should be generated when handling MAC interrupts.

Plugging in a cable happens to result in series of interrupts changing
driver's link state a number of times before finally staying at link
up (e.g. link up, link down, link up, link down, ..., link up).  To
prevent sending series of redundant IB_EVENT_PORT_ACTIVE and
IB_EVENT_PORT_ERR events, we use a timer to debounce them in
nes_port_ibevent().

Signed-off-by: Maciej Sosnowski <maciej.sosnowski@intel.com>
Signed-off-by: Roland Dreier <rolandd@cisco.com>