media: Documentation: st-vgxy61: Fix driver specific documentation not being included in the index

Fixes: 2378be89 ("media: Documentation: Add ST VGXY61 driver documentation")
Reported-by: kernel test robot <lkp@intel.com>
Signed-off-by: Benjamin Mugnier <benjamin.mugnier@foss.st.com>
Signed-off-by: Sakari Ailus <sakari.ailus@linux.intel.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@kernel.org>

Documentation/userspace-api/media/drivers/index.rst

@@ -39,4 +39,5 @@ For more details see the file COPYING in the source distribution of Linux.
 	max2175
 	meye-uapi
 	omap3isp-uapi
+	st-vgxy61
 	uvcvideo