9p: Remove p9_idpool

There are no more users left of the p9_idpool; delete it.

Link: http://lkml.kernel.org/r/20180711210225.19730-7-willy@infradead.org
Signed-off-by: Matthew Wilcox <willy@infradead.org>
Cc: Eric Van Hensbergen <ericvh@gmail.com>
Cc: Ron Minnich <rminnich@sandia.gov>
Cc: Latchesar Ionkov <lucho@ionkov.net>
Signed-off-by: Dominique Martinet <dominique.martinet@cea.fr>

include/net/9p/9p.h

@@ -561,16 +561,8 @@ struct p9_fcall {
 	u8 *sdata;
 };
 
-struct p9_idpool;
-
 int p9_errstr2errno(char *errstr, int len);
 
-struct p9_idpool *p9_idpool_create(void);
-void p9_idpool_destroy(struct p9_idpool *);
-int p9_idpool_get(struct p9_idpool *p);
-void p9_idpool_put(int id, struct p9_idpool *p);
-int p9_idpool_check(int id, struct p9_idpool *p);
-
 int p9_error_init(void);
 int p9_trans_fd_init(void);
 void p9_trans_fd_exit(void);