[PATCH] avm: fix sparse warning using integer as NULL pointer

drivers/isdn/hardware/avm/b1isa.c:206:37: warning: Using plain integer as NULL pointer drivers/isdn/hardware/avm/b1isa.c:208:33: warning: Using plain integer as NULL pointer drivers/isdn/hardware/avm/b1.c:664:42: warning: Using plain integer as NULL pointer

[PATCH] avm: fix sparse warning using integer as NULL pointer

drivers/isdn/hardware/avm/b1isa.c:206:37: warning: Using plain integer as NULL pointer drivers/isdn/hardware/avm/b1isa.c:208:33: warning: Using plain integer as NULL pointer drivers/isdn/hardware/avm/b1.c:664:42: warning: Using plain integer as NULL pointer