media: imx: imx7-media-csi: Move variable to loop scope

The phys variable is only used as a local loop variable in
imx7_csi_setup_vb2_buf(), with each entry in the array being used in the
corresponding iteration of the loop only. Move it to loop scope,
simplifying the array to a single variable.

Signed-off-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Reviewed-by: Paul Elder <paul.elder@ideasonboard.com>
Acked-by: Rui Miguel Silva <rmfrfs@gmail.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@kernel.org>