mISDN: Rework of LED status display for HFC-4S/8S/E1 cards.

LEDs will show RED if layer 1 is disabled or fails.
LEDs will show GREEN if layer 1 is active.
LEDs will blink if traffic on D-channel.

Signed-off-by: Andreas Eversberg <jolly@eversberg.eu>
Signed-off-by: Karsten Keil <keil@b1-systems.de>
Signed-off-by: David S. Miller <davem@davemloft.net>