Implement (slightly) delayed entry into ELP. This will cure several
problems:
  - It works around a firmware race condition if ELP is entered too fast
    after commands (resulting in ELP timeout -traces)
  - It will reduce the number of sleep-wake cycles between already
    scheduled events such as interrupts and tx, hence improving
    performance (less delay in switching between RX and TX)
Signed-off-by: NJuuso Oikarinen <juuso.oikarinen@nokia.com>
Reviewed-by: NVidhya Govindan <vidhya.govindan@nokia.com>
Signed-off-by: NKalle Valo <kalle.valo@nokia.com>
Signed-off-by: NJohn W. Linville <linville@tuxdriver.com>