doc: add vdev doxygen

The APIs in the rte_bus_vdev.h file were not part of the API
documentation. I added this header file to the doxygen config file with
the name vdev.

Signed-off-by: Aideen McLoughlin <aideen.mcloughlin@intel.com>
Acked-by: Ferruh Yigit <ferruh.yigit@intel.com>

doc/api/doxy-api-index.md

@@ -31,6 +31,7 @@ The public API headers are grouped by topics:
   [latency]            (@ref rte_latencystats.h),
   [devargs]            (@ref rte_devargs.h),
   [PCI]                (@ref rte_pci.h),
+  [vdev]               (@ref rte_bus_vdev.h),
   [vfio]               (@ref rte_vfio.h)
 
 - **device specific**:

doc/api/doxy-api.conf.in

@@ -4,6 +4,7 @@
 PROJECT_NAME            = DPDK
 PROJECT_NUMBER          = @VERSION@
 INPUT                   = @TOPDIR@/doc/api/doxy-api-index.md \
+                          @TOPDIR@/drivers/bus/vdev \
                           @TOPDIR@/drivers/crypto/scheduler \
                           @TOPDIR@/drivers/mempool/dpaa2 \
                           @TOPDIR@/drivers/net/bnxt \

drivers/bus/vdev/rte_bus_vdev.h

@@ -5,6 +5,12 @@
 #ifndef RTE_VDEV_H
 #define RTE_VDEV_H
 
+/**
+ * @file
+ * RTE virtual bus API
+ *
+ */
+
 #ifdef __cplusplus
 extern "C" {
 #endif