[media] media-ioc-g-topology.rst: fix typos

Fix what seems to be a few typos induced by copy/paste.

[mchehab@s-opensource.com: fix a typo]
Signed-off-by: Alexandre Courbot <acourbot@chromium.org>
Signed-off-by: Mauro Carvalho Chehab <mchehab@s-opensource.com>