isdn/eicon: use standard __init,__exit function markup

Remove the custom DIVA_{INIT,EXIT}_FUNCTION defines and use
the standard __init,__exit markup.

Signed-off-by: H Hartley Sweeten <hsweeten@visionengravers.com>
Cc: Armin Schindler <mac@melware.de>
Cc: Karsten Keil <isdn@linux-pingi.de>
Signed-off-by: David S. Miller <davem@davemloft.net>