virtio-pci: define type and header for PCI vendor data

Added macro definition for VIRTIO_PCI_CAP_VENDOR_CFG to identify the PCI
vendor data type in the virtio_pci_cap structure. Defined a new struct
virtio_pci_vndr_data for the vendor data capability header as per the
specification.

Acked-by: Jason Wang <jasowang@redhat.com>
Signed-off-by: Shijith Thotton <sthotton@marvell.com>
Message-Id: <20250103153226.1933479-3-sthotton@marvell.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>

Author: Shijith Thotton

include/uapi/linux/virtio_pci.h

@@ -116,6 +116,8 @@
 #define VIRTIO_PCI_CAP_PCI_CFG		5
 /* Additional shared memory capability */
 #define VIRTIO_PCI_CAP_SHARED_MEMORY_CFG 8
+/* PCI vendor data configuration */
+#define VIRTIO_PCI_CAP_VENDOR_CFG	9
 
 /* This is the PCI capability header: */
 struct virtio_pci_cap {
@@ -130,6 +132,18 @@ struct virtio_pci_cap {
 	__le32 length;		/* Length of the structure, in bytes. */
 };
 
+/* This is the PCI vendor data capability header: */
+struct virtio_pci_vndr_data {
+	__u8 cap_vndr;		/* Generic PCI field: PCI_CAP_ID_VNDR */
+	__u8 cap_next;		/* Generic PCI field: next ptr. */
+	__u8 cap_len;		/* Generic PCI field: capability length */
+	__u8 cfg_type;		/* Identifies the structure. */
+	__u16 vendor_id;	/* Identifies the vendor-specific format. */
+	/* For Vendor Definition */
+	/* Pads structure to a multiple of 4 bytes */
+	/* Reads must not have side effects */
+};
+
 struct virtio_pci_cap64 {
 	struct virtio_pci_cap cap;
 	__le32 offset_hi;             /* Most sig 32 bits of offset */