media: dt-bindings: schema indentation fixes

Fix a few new indentation warnings found with yamllint (now integrated
into the checks).

Cc: Ricardo Ribalda <ribalda@kernel.org>
Signed-off-by: Rob Herring <robh@kernel.org>
Acked-by: Jacopo Mondi <jacopo+renesas@jmondi.org>
Acked-by: Hans Verkuil <hverkuil-cisco@xs4all.nl> # For adv7604
Acked-by: Sakari Ailus <sakari.ailus@linux.intel.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab+huawei@kernel.org>