app/testpmd: return if no packets in GRO heavy weight mode

[ upstream commit 0007e4045c9efe6a20ad2590dfa68a86cc778b48 ]

If there are no packets flushed in GRO heavy weight mode,
return false as this fall through code would return true
indicating that packets are available

Fixes: 461c287ab553 ("app/testpmd: fix GRO packets flush on timeout")

Signed-off-by: Kumara Parameshwaran <kumaraparamesh92@gmail.com>
Reviewed-by: Ferruh Yigit <ferruh.yigit@amd.com>

app/test-pmd/csumonly.c

@@ -1137,6 +1137,8 @@ pkt_burst_checksum_forward(struct fwd_stream *fs)
 						gro_pkts_num);
 				fs->gro_times = 0;
 			}
+			if (nb_rx == 0)
+				return;
 		}
 
 		pkts_ip_csum_recalc(pkts_burst, nb_rx, tx_offloads);