media: vimc: Remove unneeded return statement in vimc_sen_s_stream()

The other subdevice implementations in vimc (debayer and scaler) which
share their code structure with the sensor do not have an explicit
return statement at the end of the s_stream(0) code path. Align the
sensor subdevice by dropping the return statement.

Signed-off-by: Niklas Söderlund <niklas.soderlund+renesas@ragnatech.se>
Signed-off-by: Hans Verkuil <hverkuil-cisco@xs4all.nl>
Signed-off-by: Mauro Carvalho Chehab <mchehab+samsung@kernel.org>