media: rkisp1: isp: Don't initialize ret to 0 in rkisp1_isp_s_stream()

The ret variable doesn't need to be initialized in
rkisp1_isp_s_stream().

Signed-off-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Reviewed-by: Dafna Hirschfeld <dafna@fastmail.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@kernel.org>