mISDN: consistently define 'debug' as '*u_int'

Impact: change data type for variable 'debug' from *int to *u_int,
same for the argument type of mISDN_inittimer

In "core.h" mISDN_inittimer is declared with the argument type "*u_int", make
the definition in "timerdev.c" match this.

This fixes also this warnings:

  drivers/isdn/mISDN/layer1.c:391:8: warning: incorrect type in assignment (different signedness)
  drivers/isdn/mISDN/layer1.c:391:8:    expected int *static [toplevel] debug
  drivers/isdn/mISDN/layer1.c:391:8:    got unsigned int [usertype] *deb
  drivers/isdn/mISDN/layer2.c:2200:8: warning: incorrect type in assignment (different signedness)
  drivers/isdn/mISDN/layer2.c:2200:8:    expected int *static [toplevel] debug
  drivers/isdn/mISDN/layer2.c:2200:8:    got unsigned int [usertype] *deb
  drivers/isdn/mISDN/socket.c:769:8: warning: incorrect type in assignment (different signedness)
  drivers/isdn/mISDN/socket.c:769:8:    expected int *static [toplevel] debug
  drivers/isdn/mISDN/socket.c:769:8:    got unsigned int [usertype] *deb

Signed-off-by: Hannes Eder <hannes@hanneseder.net>
Acked-by: Karsten Keil <kkeil@suse.de>
Signed-off-by: David S. Miller <davem@davemloft.net>