media: docs: Fix newline typo

Fix example code which has missing or double backslash typo.

Signed-off-by: Kwang Son <dev.kwang.son@gmail.com>
Signed-off-by: Hans Verkuil <hverkuil-cisco@xs4all.nl>
Signed-off-by: Mauro Carvalho Chehab <mchehab+huawei@kernel.org>