monitor: Add ringbuf_write and ringbuf_read argument completion

Export chr_is_ringbuf() function. Also remove left-over function prototypes
while at it.

Signed-off-by: Hani Benhabiles <hani@linux.com>
Signed-off-by: Luiz Capitulino <lcapitulino@redhat.com>
diff --git a/hmp.h b/hmp.h
index aba59e9..212e5d2 100644
--- a/hmp.h
+++ b/hmp.h
@@ -103,5 +103,7 @@
 void set_link_completion(ReadLineState *rs, int nb_args, const char *str);
 void netdev_add_completion(ReadLineState *rs, int nb_args, const char *str);
 void netdev_del_completion(ReadLineState *rs, int nb_args, const char *str);
+void ringbuf_write_completion(ReadLineState *rs, int nb_args, const char *str);
+void ringbuf_read_completion(ReadLineState *rs, int nb_args, const char *str);
 
 #endif