media: rkisp1: csi: Handle CSI-2 RX configuration fully in rkisp1-csi.c

The ISP layer now calls multiple functions of the CSI-2 RX layer to
configure, start and stop it, with the steps for the last two
operations. Move those calls to rkisp1_mipi_csi2_start() and
rkisp1_mipi_csi2_stop() to simplify the ISP code and the API exposed by
the CSI-2 receiver component.

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>