virtio_net: fix dma hang issue for multiseg pkts

For multi-seg pkts where pkt len is equal to total length of
required virtio descriptor buffers, an additional dma is triggered
for 0 length.
A fix is added in calculation of required buffers.

Fixes: 3660e13 ("virtio_net: fix vring desc length calculation")

Signed-off-by: Rahul Bhansali <rbhansali@marvell.com>
Change-Id: I897d9be5013446f1df5df93baee1f775e1735ed4
Reviewed-on: https://sj1git1.cavium.com/c/IP/SW/dataplane/dpu-offload/+/134042
Tested-by: sa_ip-toolkits-Jenkins <sa_ip-toolkits-jenkins@marvell.com>
Reviewed-by: Nithin Kumar Dabilpuram <ndabilpuram@marvell.com>

lib/virtio_net/virtio_net_enq.c

@@ -145,7 +145,7 @@ calculate_nb_enq(uint64_t *sd_desc_base, uint16_t off, uint32_t slen, uint16_t q
 	uint32_t dlen = 0;
 	uint64_t d_flags;
 
-	while (dlen <= slen && avail_sd) {
+	while (dlen < slen && avail_sd) {
 		d_flags = *DESC_PTR_OFF(sd_desc_base, off, 8);
 		dlen += d_flags & (RTE_BIT64(32) - 1);
 		off = (off + 1) & (qsize - 1);