doc: Move vhost doc from modules to user guides

This is a user guide, so move it to the right spot.

Change-Id: I8e50fdb95e6a982b444efd0e0ae55cd4b43e3017
Signed-off-by: Ben Walker <benjamin.walker@intel.com>
Reviewed-on: https://review.gerrithub.io/397636
Tested-by: SPDK Automated Test System <sys_sgsw@intel.com>
Reviewed-by: Dariusz Stojaczyk <dariuszx.stojaczyk@intel.com>
Reviewed-by: Daniel Verkamp <daniel.verkamp@intel.com>
Reviewed-by: Jim Harris <james.r.harris@intel.com>

doc/index.md

@@ -20,6 +20,7 @@
 
 - @ref iscsi
 - @ref nvmf
+- @ref vhost
 - @ref bdev
 - @ref blobfs
 - @ref jsonrpc
@@ -37,7 +38,7 @@
 - @ref nvme
 - @ref ioat
 - @ref blob
-- @ref vhost
+
 - @ref virtio
 
 # Tools {#tools}

doc/vhost.md

@@ -1,4 +1,4 @@
-# vhost {#vhost}
+# vhost Target {#vhost}
 
 # Table of Contents {#vhost_toc}