[intelxl] Allow admin cookie to hold extended opcode and return code

The "send to PF" and "send to VF" admin queue descriptors (ab)use the
cookie field to hold the extended opcode and return code values.

Signed-off-by: Michael Brown <mcb30@ipxe.org>

src/drivers/net/intelxl.h

@@ -333,10 +333,15 @@ struct intelxl_admin_descriptor {
 	uint16_t len;
 	/** Return value */
 	uint16_t ret;
-	/** Cookie */
-	uint32_t cookie;
-	/** Reserved */
-	uint32_t reserved;
+	/** Opaque cookie / VF opcode */
+	union {
+		/** Cookie */
+		uint32_t cookie;
+		/** VF opcode */
+		uint32_t vopcode;
+	};
+	/** VF return value */
+	int32_t vret;
 	/** Parameters */
 	union intelxl_admin_params params;
 } __attribute__ (( packed ));