[PATCH] teach seq_file to discard entries

Allow ->show() return SEQ_SKIP; that will discard all
output from that element and move on.

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

include/linux/seq_file.h

@@ -30,6 +30,8 @@ struct seq_operations {
 	int (*show) (struct seq_file *m, void *v);
 };
 
+#define SEQ_SKIP 1
+
 int seq_open(struct file *, const struct seq_operations *);
 ssize_t seq_read(struct file *, char __user *, size_t, loff_t *);
 loff_t seq_lseek(struct file *, loff_t, int);