media: rcar-vin: Cleanup notifier in error path

During the notifier initialization, memory for the list of associated async
subdevices is reserved during the fwnode endpoint parsing from the v4l2-async
framework. If the notifier registration fails, that memory should be released
and the notifier 'cleaned up'.

Catch the notifier registration error and perform the cleanup both for the
group and the parallel notifiers.

Signed-off-by: Jacopo Mondi <jacopo+renesas@jmondi.org>
Acked-by: Niklas Söderlund <niklas.soderlund+renesas@ragnatech.se>
Signed-off-by: Hans Verkuil <hans.verkuil@cisco.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab+samsung@kernel.org>