virtio: pci: Fix discovery of device config length

The length of the device config was erroneously being taken from the
notify capability. Correct this by finding the length in the device
capability.

Fixes: 550435edf810 ("virtio: pci: Support non-legacy PCI transport device")
Signed-off-by: Andrew Scull <ascull@google.com>
Reviewed-by: Bin Meng <bmeng.cn@gmail.com>
diff --git a/drivers/virtio/virtio_pci_modern.c b/drivers/virtio/virtio_pci_modern.c
index fd8a1f3..55d25cb 100644
--- a/drivers/virtio/virtio_pci_modern.c
+++ b/drivers/virtio/virtio_pci_modern.c
@@ -497,7 +497,7 @@
 	 */
 	device = virtio_pci_find_capability(udev, VIRTIO_PCI_CAP_DEVICE_CFG);
 	if (device) {
-		offset = notify + offsetof(struct virtio_pci_cap, length);
+		offset = device + offsetof(struct virtio_pci_cap, length);
 		dm_pci_read_config32(udev, offset, &priv->device_len);
 	}