media: vidioc-g-fmt.rst: adjust table format

While doing a visual inspection with Sphinx 1.5, I noticed that
one of the columns was smaller than the text written there.

As this is the only thing I noticed with Sphinx 1.5, I suspect
that this was also a problem with Sphinx 1.4. Yet, I opted to
touch it in a way that wouldn't cause backward issues.
Signed-off-by: Mauro Carvalho Chehab <mchehab@s-opensource.com>

Documentation/media/uapi/v4l/vidioc-g-fmt.rst

@@ -88,7 +88,7 @@ The format as returned by :ref:`VIDIOC_TRY_FMT <VIDIOC_G_FMT>` must be identical
 
 .. c:type:: v4l2_format
 
-.. tabularcolumns::  |p{1.2cm}|p{4.3cm}|p{3.0cm}|p{9.0cm}|
+.. tabularcolumns::  |p{1.2cm}|p{4.6cm}|p{3.0cm}|p{8.6cm}|
 
 .. flat-table:: struct v4l2_format
     :header-rows:  0