media: vidioc-queryctrl.rst: fix error code

An attempt to get a BUTTON control returns EACCES, not EINVAL.

BUTTON controls have V4L2_CTRL_FLAG_WRITE_ONLY set, and the documentation
for that flag correctly says that getting a write-only control returns
EACCES. It's the description of the BUTTON type that's wrong, so fix
that so they are consistent.
Signed-off-by: Hans Verkuil <hverkuil-cisco@xs4all.nl>
Signed-off-by: Mauro Carvalho Chehab <mchehab+huawei@kernel.org>

Documentation/media/uapi/v4l/vidioc-queryctrl.rst

@@ -378,7 +378,7 @@ See also the examples in :ref:`control`.
       - 0
       - 0
       - A control which performs an action when set. Drivers must ignore
-	the value passed with ``VIDIOC_S_CTRL`` and return an ``EINVAL`` error
+	the value passed with ``VIDIOC_S_CTRL`` and return an ``EACCES`` error
 	code on a ``VIDIOC_G_CTRL`` attempt.
     * - ``V4L2_CTRL_TYPE_INTEGER64``
       - any