ieee1394: nodemgr: make module parameter ignore_drivers writable

Nodemgr's ignore_drivers variable is exposed as a module load parameter
(therefore also as a sysfs attribute below /sys/module) and additionally
as an attribute below /sys/bus/ieee1394.  Since the latter is writable,
make the former writable too.

Note, the bus's attribute ignore_drivers is only relevant to newly added
units, not to present or suspended or resuming units.  Those have their
own attribute ignore_driver.

Signed-off-by: Stefan Richter <stefanr@s5r6.in-berlin.de>
Index: linux/drivers/ieee1394/nodemgr.c
===================================================================
--- linux.orig/drivers/ieee1394/nodemgr.c	2006-07-01 21:17:37.000000000 +0200
+++ linux/drivers/ieee1394/nodemgr.c	2006-07-01 21:21:23.000000000 +0200
@@ -28,7 +28,7 @@
 #include "nodemgr.h"
 
 static int ignore_drivers;
-module_param(ignore_drivers, int, 0444);
+module_param(ignore_drivers, int, S_IRUGO | S_IWUSR);
 MODULE_PARM_DESC(ignore_drivers, "Disable automatic probing for drivers.");
 
 struct nodemgr_csr_info {