switch aio and shm to do_mmap_pgoff(), make do_mmap() static

after all, 0 bytes and 0 pages is the same thing...

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
diff --git a/ipc/shm.c b/ipc/shm.c
index e3a8063..5e2cbfd 100644
--- a/ipc/shm.c
+++ b/ipc/shm.c
@@ -1054,7 +1054,7 @@
 			goto invalid;
 	}
 		
-	user_addr = do_mmap (file, addr, size, prot, flags, 0);
+	user_addr = do_mmap_pgoff(file, addr, size, prot, flags, 0);
 	*raddr = user_addr;
 	err = 0;
 	if (IS_ERR_VALUE(user_addr))