media: imx: imx7_mipi_csis: Make ISP registers macros take channel ID

Replace the per-channel ISP registers macros with a single one that take
the channel as a parameter. Only channel 0 is supported for now, but
this will make support for multiple channels easier.

Signed-off-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Reviewed-by: Rui Miguel Silva <rmfrfs@gmail.com>
Signed-off-by: Hans Verkuil <hverkuil-cisco@xs4all.nl>
Signed-off-by: Mauro Carvalho Chehab <mchehab+huawei@kernel.org>