kill find_inode_number()

the only remaining caller (in ncpfs) is guaranteed to return 0 -
we only hit it if we'd just checked that there's no dentry with
such name.

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

include/linux/fs.h

@@ -2311,7 +2311,6 @@ extern struct file * open_exec(const char *);
 /* fs/dcache.c -- generic fs support functions */
 extern int is_subdir(struct dentry *, struct dentry *);
 extern int path_is_under(struct path *, struct path *);
-extern ino_t find_inode_number(struct dentry *, struct qstr *);
 
 #include <linux/err.h>