proc_fops: convert drivers/isdn/ to seq_file

Convert code away from ->read_proc/->write_proc interfaces.  Switch to
proc_create()/proc_create_data() which make addition of proc entries
reliable wrt NULL ->proc_fops, NULL ->data and so on.

Problem with ->read_proc et al is described here commit
786d7e1612 "Fix rmmod/read/write races in
/proc entries"

[akpm@linux-foundation.org: CONFIG_PROC_FS=n build fix]
Signed-off-by: Alexey Dobriyan <adobriyan@gmail.com>
Signed-off-by: Tilman Schmidt <tilman@imap.cc>
Signed-off-by: Karsten Keil <keil@b1-systems.de>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/isdn/hardware/avm/t1pci.c

@@ -119,7 +119,7 @@ static int t1pci_add_card(struct capicardparams *p, struct pci_dev *pdev)
 	cinfo->capi_ctrl.load_firmware = b1dma_load_firmware;
 	cinfo->capi_ctrl.reset_ctr     = b1dma_reset_ctr;
 	cinfo->capi_ctrl.procinfo      = t1pci_procinfo;
-	cinfo->capi_ctrl.ctr_read_proc = b1dmactl_read_proc;
+	cinfo->capi_ctrl.proc_fops = &b1dmactl_proc_fops;
 	strcpy(cinfo->capi_ctrl.name, card->name);
 
 	retval = attach_capi_ctr(&cinfo->capi_ctrl);