media: ipu3-cio2: Unregister device nodes first, then release resources

While there are issues related to object lifetime management, unregister
the media device first, followed immediately by other device nodes when
the driver is being unbound. Only then the resources needed by the driver
may be released. This is slightly safer.

Signed-off-by: Sakari Ailus <sakari.ailus@linux.intel.com>
Tested-by: Bingbu Cao <bingbu.cao@intel.com>
Reviewed-by: Bingbu Cao <bingbu.cao@intel.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab+samsung@kernel.org>