[media] Add multi-planar API documentation

Add DocBook documentation for the new multi-planar API extensions to the
Video for Linux 2 API DocBook.

Signed-off-by: Pawel Osciak <pawel@osciak.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>
diff --git a/Documentation/DocBook/v4l/vidioc-enum-fmt.xml b/Documentation/DocBook/v4l/vidioc-enum-fmt.xml
index 960d446..71d373b 100644
--- a/Documentation/DocBook/v4l/vidioc-enum-fmt.xml
+++ b/Documentation/DocBook/v4l/vidioc-enum-fmt.xml
@@ -76,7 +76,9 @@
 	    <entry>Type of the data stream, set by the application.
 Only these types are valid here:
 <constant>V4L2_BUF_TYPE_VIDEO_CAPTURE</constant>,
+<constant>V4L2_BUF_TYPE_VIDEO_CAPTURE_MPLANE</constant>,
 <constant>V4L2_BUF_TYPE_VIDEO_OUTPUT</constant>,
+<constant>V4L2_BUF_TYPE_VIDEO_OUTPUT_MPLANE</constant>,
 <constant>V4L2_BUF_TYPE_VIDEO_OVERLAY</constant>, and custom (driver
 defined) types with code <constant>V4L2_BUF_TYPE_PRIVATE</constant>
 and higher.</entry>