media: media-types.rst: fix doc warnings

Fix these warnings when building the documentation:

media.h.rst:6: WARNING: undefined label: media-ent-f-dv-decoder (if the link has no caption the label must precede a section header)
media.h.rst:6: WARNING: undefined label: media-ent-f-dv-encoder (if the link has no caption the label must precede a section header)
media.h.rst:6: WARNING: undefined label: media-ent-f-dv-decoder (if the link has no caption the label must precede a section header)

Signed-off-by: Hans Verkuil <hans.verkuil@cisco.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab+samsung@kernel.org>

Documentation/media/uapi/mediactl/media-types.rst

@@ -41,7 +41,8 @@ Types and flags used to represent the media graph elements
 .. _MEDIA-ENT-F-PROC-VIDEO-DECODER:
 .. _MEDIA-ENT-F-VID-MUX:
 .. _MEDIA-ENT-F-VID-IF-BRIDGE:
-.. _MEDIA-ENT-F-DTV-DECODER:
+.. _MEDIA-ENT-F-DV-DECODER:
+.. _MEDIA-ENT-F-DV-ENCODER:
 
 .. cssclass:: longtable