bna: Add RX State

bna: Add RX State

Change Details:
 -      BNA state machine for Rx in start_wait state moves it to stop_wait on
        receipt of RX_E_STOP. In Rx stop_wait state, on receipt of
                RX_E_STARTED event does enet stop
                RX_E_STOPPED event does rx_cleanup_cbfn
        rx_cleanup_cbfn in this case is called without post_cbfn. post_cbfn
        happens only after RX_E_STARTED event is received in start_wait. Without
        doing post_cbfn, NAPI remains disabled and in cleanup we try to disable
        again causing endless wait. ifconfig process and other workers can thus
        get stuck.
 -      Introducing start_stop_wait state for Rx. This state handles the case of
        if post_cbfn is not done simply do stop without the cleanup.

Signed-off-by: Rasesh Mody <rmody@brocade.com>
Signed-off-by: David S. Miller <davem@davemloft.net>