um: hostfs: Reduce number of syscalls in readdir

Currently hostfs issues every time a seekdir(), in fact
it has to do this only upon the first call.
Also telldir() can be omitted as we can obtain the directory
offset from readdir().

Signed-off-by: Richard Weinberger <richard@nod.at>
diff --git a/fs/hostfs/hostfs.h b/fs/hostfs/hostfs.h
index 493262e..91e19f9 100644
--- a/fs/hostfs/hostfs.h
+++ b/fs/hostfs/hostfs.h
@@ -66,7 +66,8 @@
 extern int access_file(char *path, int r, int w, int x);
 extern int open_file(char *path, int r, int w, int append);
 extern void *open_dir(char *path, int *err_out);
-extern char *read_dir(void *stream, unsigned long long *pos,
+extern void seek_dir(void *stream, unsigned long long pos);
+extern char *read_dir(void *stream, unsigned long long *pos_out,
 		      unsigned long long *ino_out, int *len_out,
 		      unsigned int *type_out);
 extern void close_file(void *stream);