[PATCH hurd] Comment fixes

[Zhaoming Luo]

I don't think ioctls.h is a good place looking for the subsystem id
calculation, instead hurd/ioctls.defs, it contains the following codes:

```
/* Calculate the MiG subsystem (i.e. first message ID)
   for the RPCs produced by ioctl requests in the given group.  */
#define IOC_GROUP_SUBSYSTEM(group)      (100000 + ((group) - 'f') * 4000)
```

---
 hurd/iioctl.defs  | 4 ++--
 hurd/kdioctl.defs | 4 ++--
 hurd/rioctl.defs  | 4 ++--
 hurd/tioctl.defs  | 4 ++--
 4 files changed, 8 insertions(+), 8 deletions(-)

diff --git a/hurd/iioctl.defs b/hurd/iioctl.defs
index 58b7dbab..30087fea 100644
--- a/hurd/iioctl.defs
+++ b/hurd/iioctl.defs
@@ -17,8 +17,8 @@ You should have received a copy of the GNU General Public 
License
 along with the GNU Hurd; see the file COPYING.  If not, write to
 the Free Software Foundation, 675 Mass Ave, Cambridge, MA 02139, USA.  */
 
-/* Ioctl class `i'; the subsystem is derived from calculations in
-   <ioctls.h>. */
+/* Ioctl class `i'; the subsystem is derived from IOC_GROUP_SUBSYSTEM in
+   hurd/ioctls.defs. */
 subsystem iioctl 112000; /* XXX */
 
 #include <hurd/ioctl_types.defs>
diff --git a/hurd/kdioctl.defs b/hurd/kdioctl.defs
index 0dd09d38..88f69496 100644
--- a/hurd/kdioctl.defs
+++ b/hurd/kdioctl.defs
@@ -17,8 +17,8 @@ You should have received a copy of the GNU General Public 
License
 along with the GNU Hurd; see the file COPYING.  If not, write to
 the Free Software Foundation, 675 Mass Ave, Cambridge, MA 02139, USA.  */
 
-/* Ioctl class `k'; the subsystem is derived from calculations in
-   <ioctls.h>. */
+/* Ioctl class `k'; the subsystem is derived from IOC_GROUP_SUBSYSTEM in
+   hurd/ioctls.defs. */
 subsystem kdioctl 120000;
 
 #include <hurd/hurd_types.defs>
diff --git a/hurd/rioctl.defs b/hurd/rioctl.defs
index e04fe6b3..880c087a 100644
--- a/hurd/rioctl.defs
+++ b/hurd/rioctl.defs
@@ -18,8 +18,8 @@ along with the GNU Hurd; see the file COPYING.  If not, write 
to
 the Free Software Foundation, 675 Mass Ave, Cambridge, MA 02139, USA.  */
 
 
-/* Ioctl class `r'; the subsystem is derived from calculations in
-   <ioctls.h>. */
+/* Ioctl class `r'; the subsystem is derived from IOC_GROUP_SUBSYSTEM in
+   hurd/ioctls.defs. */
 subsystem rioctl 148000; /* XXX */
 
 #include <hurd/ioctl_types.defs>
diff --git a/hurd/tioctl.defs b/hurd/tioctl.defs
index 905a4a38..74af62e2 100644
--- a/hurd/tioctl.defs
+++ b/hurd/tioctl.defs
@@ -17,8 +17,8 @@ You should have received a copy of the GNU General Public 
License
 along with the GNU Hurd; see the file COPYING.  If not, write to
 the Free Software Foundation, 675 Mass Ave, Cambridge, MA 02139, USA.  */
 
-/* Ioctl class `t'; the subsystem is derived from calculations in
-   <ioctls.h>. */
+/* Ioctl class `t'; the subsystem is derived from IOC_GROUP_SUBSYSTEM in
+   hurd/ioctls.defs. */
 subsystem tioctl 156000; /* XXX */
 
 #include <hurd/hurd_types.defs>
-- 
2.47.0