CLEANUP: mux-quic: remove unused fields for Rx

Rx has been simplified since the conversion of buffer to a ncbuf. The
old buffer can now be removed. The frms tree is also removed. It was
used previously to stored out-of-order received STREAM frames. Now the
MUX is able to buffer them directly into the ncbuf.
diff --git a/include/haproxy/mux_quic-t.h b/include/haproxy/mux_quic-t.h
index d096d1d..ddd19d3 100644
--- a/include/haproxy/mux_quic-t.h
+++ b/include/haproxy/mux_quic-t.h
@@ -101,9 +101,7 @@
 	void *ctx;           /* app-ops context */
 
 	struct {
-		struct eb_root frms; /* received frames ordered by their offsets */
 		uint64_t offset; /* absolute current base offset of ncbuf */
-		struct buffer buf; /* receive buffer, always valid (buf_empty or real buffer) */
 		struct ncbuf ncbuf; /* receive buffer - can handle out-of-order offset frames */
 		struct buffer app_buf; /* receive buffer used by conn_stream layer */
 		uint64_t msd; /* fctl bytes limit to enforce */
diff --git a/src/mux_quic.c b/src/mux_quic.c
index 022b1db..f5de551 100644
--- a/src/mux_quic.c
+++ b/src/mux_quic.c
@@ -153,11 +153,9 @@
 	qcs->tx.msd = quic_stream_is_local(qcc, id) ? qcc->rfctl.msd_bidi_r :
 	                                              qcc->rfctl.msd_bidi_l;
 
-	qcs->rx.buf = BUF_NULL;
 	qcs->rx.ncbuf = NCBUF_NULL;
 	qcs->rx.app_buf = BUF_NULL;
 	qcs->rx.offset = 0;
-	qcs->rx.frms = EB_ROOT_UNIQUE;
 
 	/* TODO use uni limit for unidirectional streams */
 	qcs->rx.msd = quic_stream_is_local(qcc, id) ? qcc->lfctl.msd_bidi_l :
@@ -202,7 +200,6 @@
  */
 void qcs_free(struct qcs *qcs)
 {
-	b_free(&qcs->rx.buf);
 	qc_free_ncbuf(qcs, &qcs->rx.ncbuf);
 	b_free(&qcs->tx.buf);