media: MAINTAINERS: add entry for Rockchip ISP1 driver

Add MAINTAINERS entry for the rockchip isp1 driver.

Signed-off-by: Helen Koike <helen.koike@collabora.com>
Signed-off-by: Hans Verkuil <hverkuil-cisco@xs4all.nl>
Signed-off-by: Mauro Carvalho Chehab <mchehab+huawei@kernel.org>