media: staging: media: imx: imx7_mipi_csis: Store colorspace in set_fmt as well

Without this the default (SMPTE 170M) from init_cfg stays unchanged.
Even after configuring 'srgb' colorspace (or 'raw')
$ media-ctl -V "'csis-32e30000.mipi-csi':0 [colorspace:srgb]"
the colorspace does not change at all:
$ media-ctl --get-v4l2 "'csis-32e30000.mipi-csi':0"
  [fmt:SRGGB10_1X10/1920x1080 field:none colorspace:smpte170m xfer:709
   ycbcr:601 quantization:lim-range]

Signed-off-by: Alexander Stein <alexander.stein@ew.tq-group.com>
Signed-off-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@kernel.org>