MINOR: channel: rename bi_avail() to channel_recv_max()

This name more accurately reminds that it applies to a channel and not
to a buffer, and that what is returned may be used as a max number of
bytes to pass to recv().
diff --git a/include/proto/channel.h b/include/proto/channel.h
index 15ff1a9..db179ca 100644
--- a/include/proto/channel.h
+++ b/include/proto/channel.h
@@ -324,7 +324,7 @@
  * is close to happen. The test is optimized to avoid as many operations as
  * possible for the fast case.
  */
-static inline int bi_avail(const struct channel *chn)
+static inline int channel_recv_max(const struct channel *chn)
 {
 	int ret;
 
diff --git a/src/stream_interface.c b/src/stream_interface.c
index 19adcee..f05f4a8 100644
--- a/src/stream_interface.c
+++ b/src/stream_interface.c
@@ -1181,7 +1181,7 @@
 	 * recv().
 	 */
 	while (!(conn->flags & (CO_FL_ERROR | CO_FL_SOCK_RD_SH | CO_FL_DATA_RD_SH | CO_FL_WAIT_ROOM | CO_FL_HANDSHAKE))) {
-		max = bi_avail(chn);
+		max = channel_recv_max(chn);
 
 		if (!max) {
 			si->flags |= SI_FL_WAIT_ROOM;