proc: Rename in proc_inode rename sysctl_inodes sibling_inodes

I about to need and use the same functionality for pid based
inodes and there is no point in adding a second field when
this field is already here and serving the same purporse.

Just give the field a generic name so it is clear that
it is no longer sysctl specific.

Also for good measure initialize sibling_inodes when
proc_inode is initialized.

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

fs/proc/inode.c

@@ -68,6 +68,7 @@ static struct inode *proc_alloc_inode(struct super_block *sb)
 	ei->pde = NULL;
 	ei->sysctl = NULL;
 	ei->sysctl_entry = NULL;
+	INIT_HLIST_NODE(&ei->sibling_inodes);
 	ei->ns_ops = NULL;
 	return &ei->vfs_inode;
 }