osmo_io: Make name optional, add _set_name() API

This allows renaming the iofd at any later point in time. This is useful
for instance if the parent object holding the iofd changes its name.

Change-Id: If2772a3ccaa98616e0189862a49ab0243435e343
diff --git a/include/osmocom/core/osmo_io.h b/include/osmocom/core/osmo_io.h
index d278ce0..aac25a3 100644
--- a/include/osmocom/core/osmo_io.h
+++ b/include/osmocom/core/osmo_io.h
@@ -88,5 +88,6 @@
 
 int osmo_iofd_get_fd(const struct osmo_io_fd *iofd);
 const char *osmo_iofd_get_name(const struct osmo_io_fd *iofd);
+void osmo_iofd_set_name(struct osmo_io_fd *iofd, const char *name);
 
 void osmo_iofd_set_ioops(struct osmo_io_fd *iofd, const struct osmo_io_ops *ioops);