staging: bcm2835-camera: Initialise dev in v4l2_dev

commit 98698ca upstream.

Commit 42a2f66 ("staging: vc04_services: Move global g_state to
vchiq_state") changed mmal_init to pass dev->v4l2_dev.dev to
vchiq_mmal_init, however nothing iniitialised dev->v4l2_dev, so we got
a NULL pointer dereference.

Set dev->v4l2_dev.dev during bcm2835_mmal_probe. The device pointer
could be passed into v4l2_device_register to set it, however that also
has other effects that would need additional changes.

Fixes: 42a2f66 ("staging: vc04_services: Move global g_state to vchiq_state")
Cc: stable@vger.kernel.org
Signed-off-by: Dave Stevenson <dave.stevenson@raspberrypi.com>
Reviewed-by: Stefan Wahren <wahrenst@gmx.net>
Link: https://lore.kernel.org/r/20250423-staging-bcm2835-v4l2-fix-v2-1-3227f0ba4700@raspberrypi.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/staging/vc04_services/bcm2835-camera/bcm2835-camera.c

@@ -1902,6 +1902,7 @@ static int bcm2835_mmal_probe(struct vchiq_device *device)
 				__func__, ret);
 			goto free_dev;
 		}
+		dev->v4l2_dev.dev = &device->dev;
 
 		/* setup v4l controls */
 		ret = bcm2835_mmal_init_controls(dev, &dev->ctrl_handler);