.gitignore: ignore some vhost-user* related files

Commit d52c454aad creates
'/contrib/vhost-user-gpu/50-qemu-gpu.json' and '/vhost-user-gpu'
and commit 06914c97d3 creates '/vhost-user-input' neither of
which is ignored by git.

Signed-off-by: Michal Privoznik <mprivozn@redhat.com>
Reviewed-by: Marc-André Lureau <marcandre.lureau@redhat.com>
Reviewed-by: Philippe Mathieu-Daudé <philmd@redhat.com>
Message-Id: <db150a03315a89a849ab9968e4a5a26110d41424.1562942402.git.mprivozn@redhat.com>
Signed-off-by: Laurent Vivier <laurent@vivier.eu>

.gitignore

@@ -65,6 +65,8 @@
 /scsi/qemu-pr-helper
 /vhost-user-scsi
 /vhost-user-blk
+/vhost-user-gpu
+/vhost-user-input
 /fsdev/virtfs-proxy-helper
 *.tmp
 *.[1-9]
@@ -131,6 +133,7 @@
 /docs/interop/qemu-qmp-ref.info*
 /docs/interop/qemu-qmp-ref.txt
 /docs/version.texi
+/contrib/vhost-user-gpu/50-qemu-gpu.json
 *.tps
 .stgit-*
 .git-submodule-status