[media] media: add a debug message to warn about gobj creation/removal

It helps to check if the media controller is doing the
right thing with the object creation and removal.

No extra code/data will be produced if DEBUG or
CONFIG_DYNAMIC_DEBUG is not enabled.

Acked-by: Hans Verkuil <hans.verkuil@cisco.com>
Reviewed-by: Javier Martinez Canillas <javier@osg.samsung.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@osg.samsung.com>