sysctl: fix ax25 checks

Fix:

sysctl table check failed: /net/ax25/ax0/ax25_default_mode .3.9.1.2 Unknown
sysctl binary path
Pid: 2936, comm: kissattach Not tainted 2.6.24-rc5 #1
 [<c012ca6a>] set_fail+0x3b/0x43
 [<c012ce7a>] sysctl_check_table+0x408/0x456
 [<c012ce8e>] sysctl_check_table+0x41c/0x456
 [<c012ce8e>] sysctl_check_table+0x41c/0x456
 ...

Signed-off-by: Eric W. Biederman <ebiederm@xmission.com>
Cc: Bernard Pidoux <pidoux@ccr.jussieu.fr>
Cc: "David S. Miller" <davem@davemloft.net>
Cc: "Rafael J. Wysocki" <rjw@sisk.pl>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>