Fix this warning when building the docs:

include/media/v4l2-dev.h:42: warning: Enum value 'VFL_TYPE_MAX' not described in enum 'vfl_devnode_type'
Acked-by: NSakari Ailus <sakari.ailus@linux.intel.com>
Signed-off-by: NHans Verkuil <hans.verkuil@cisco.com>
Signed-off-by: NMauro Carvalho Chehab <mchehab+samsung@kernel.org>