media: imx: imx7-media-csi: Remove unneeded register read

The imx7_csi_dma_reflash() function starts by reading the unrelated
register CSI_CSICR18 to then overwrite the read value with a read from
register CSI_CSICR3. This is likely due to a bad copy&paste, and is not
needed. Remove the extraneous read from register CSI_CSICR18.

Fixes: 9e5fa4e1 ("media: imx7-media-csi: Use u32 for storing register reads")
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>