vty: Fix warnings about undeclared functions

This commit adds missing includes to pcu_vty.c and fixes the
llist_head type (missing struct keyword) used by tbf_print_vty_info.

Sponsored-by: On-Waves ehf
diff --git a/src/tbf.h b/src/tbf.h
index e835ab6..bfe2875 100644
--- a/src/tbf.h
+++ b/src/tbf.h
@@ -406,8 +406,7 @@
 #include <osmocom/vty/command.h>
 #include <osmocom/vty/vty.h>
 
-
-	void tbf_print_vty_info(struct vty *vty, llist_head *tbf);
+	void tbf_print_vty_info(struct vty *vty, struct llist_head *tbf);
 #ifdef __cplusplus
 }
 #endif