CLEANUP: stdesc: rename the stream connector ->cs field to ->sc

This is a rename of this field. Most of the places were in muxes, but
were already factored with the previous series adding *_sc().
diff --git a/src/mux_pt.c b/src/mux_pt.c
index 4ae403d..fefccd9 100644
--- a/src/mux_pt.c
+++ b/src/mux_pt.c
@@ -94,7 +94,7 @@
 /* returns the stconn associated to the stream */
 static forceinline struct stconn *pt_sc(const struct mux_pt_ctx *pt)
 {
-	return pt->endp->cs;
+	return pt->endp->sc;
 }
 
 static inline void pt_trace_buf(const struct buffer *buf, size_t ofs, size_t len)
@@ -386,12 +386,12 @@
 	TRACE_ENTER(PT_EV_STRM_NEW, conn);
 	if (ctx->wait_event.events)
 		conn->xprt->unsubscribe(ctx->conn, conn->xprt_ctx, SUB_RETRY_RECV, &ctx->wait_event);
-	if (cs_attach_mux(endp->cs, ctx, conn) < 0)
+	if (cs_attach_mux(endp->sc, ctx, conn) < 0)
 		return -1;
 	ctx->endp = endp;
 	se_fl_set(ctx->endp, SE_FL_RCV_MORE);
 
-	TRACE_LEAVE(PT_EV_STRM_NEW, conn, endp->cs);
+	TRACE_LEAVE(PT_EV_STRM_NEW, conn, endp->sc);
 	return 0;
 }
 
@@ -428,7 +428,7 @@
 	struct connection *conn = endp->conn;
 	struct mux_pt_ctx *ctx;
 
-	TRACE_ENTER(PT_EV_STRM_END, conn, endp->cs);
+	TRACE_ENTER(PT_EV_STRM_END, conn, endp->sc);
 
 	ctx = conn->ctx;
 
@@ -438,7 +438,7 @@
 		conn->xprt->subscribe(conn, conn->xprt_ctx, SUB_RETRY_RECV, &ctx->wait_event);
 	} else {
 		/* There's no session attached to that connection, destroy it */
-		TRACE_DEVEL("killing dead connection", PT_EV_STRM_END, conn, endp->cs);
+		TRACE_DEVEL("killing dead connection", PT_EV_STRM_END, conn, endp->sc);
 		mux_pt_destroy(ctx);
 	}