sysctl: Remove dead register_sysctl_root

The function no longer does anything.  The is only a single caller of
register_sysctl_root when semantically there should be two.  Remove
this function so that if someone decides this functionality is needed
again it will be obvious all of the callers of setup_sysctl_set need
to be audited and modified appropriately.

Signed-off-by: "Eric W. Biederman" <ebiederm@xmission.com>

fs/proc/proc_sysctl.c

@@ -408,10 +408,6 @@ static void next_entry(struct ctl_table_header **phead, struct ctl_table **pentr
 	*pentry = entry;
 }
 
-void register_sysctl_root(struct ctl_table_root *root)
-{
-}
-
 /*
  * sysctl_perm does NOT grant the superuser all rights automatically, because
  * some sysctl variables are readonly even to root.