net/mlx5: fix r/w lock usage in DMA unmap

For mlx5 DMA unmap, write lock should be used for rebuilding memory
region cache table rather than read lock.

Fixes: 989e999 ("net/mlx5: support PCI device DMA map and unmap")
Cc: stable@dpdk.org

Signed-off-by: Feifei Wang <feifei.wang2@arm.com>
Reviewed-by: Ruifeng Wang <ruifeng.wang@arm.com>
Acked-by: Viacheslav Ovsiienko <viacheslavo@nvidia.com>

drivers/net/mlx5/mlx5_mr.c

@@ -304,10 +304,10 @@ mlx5_dma_unmap(struct rte_pci_device *pdev, void *addr,
 	}
 	priv = dev->data->dev_private;
 	sh = priv->sh;
-	rte_rwlock_read_lock(&sh->share_cache.rwlock);
+	rte_rwlock_write_lock(&sh->share_cache.rwlock);
 	mr = mlx5_mr_lookup_list(&sh->share_cache, &entry, (uintptr_t)addr);
 	if (!mr) {
-		rte_rwlock_read_unlock(&sh->share_cache.rwlock);
+		rte_rwlock_write_unlock(&sh->share_cache.rwlock);
 		DRV_LOG(WARNING, "address 0x%" PRIxPTR " wasn't registered "
 				 "to PCI device %p", (uintptr_t)addr,
 				 (void *)pdev);
@@ -327,7 +327,7 @@ mlx5_dma_unmap(struct rte_pci_device *pdev, void *addr,
 	++sh->share_cache.dev_gen;
 	DRV_LOG(DEBUG, "broadcasting local cache flush, gen=%d",
 	      sh->share_cache.dev_gen);
-	rte_rwlock_read_unlock(&sh->share_cache.rwlock);
+	rte_rwlock_write_unlock(&sh->share_cache.rwlock);
 	return 0;
 }