media: imx: imx7-media-csi: Don't double-enable the CSI

The CSI is enabled at the end of imx7_csi_sw_reset(), called from
imx7_csi_enable(), as well as at the end of imx7_csi_enable(). The
latter is enough, remove the former.

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>