media: imx7_mipi_csis: remove internal ops

Remove code that is not called anywhere, just
remove the internal ops.

Signed-off-by: Rui Miguel Silva <rui.silva@linaro.org>
Signed-off-by: Hans Verkuil <hverkuil-cisco@xs4all.nl>
Signed-off-by: Mauro Carvalho Chehab <mchehab+samsung@kernel.org>