media: vidioc-dqevent.rst: clarify V4L2_EVENT_SRC_CH_RESOLUTION

Clarify that when you receive V4L2_EVENT_SOURCE_CHANGE with flag
V4L2_EVENT_SRC_CH_RESOLUTION set, and the new resolution appears
identical to the old resolution, then you still must restart the
streaming I/O.

Signed-off-by: Hans Verkuil <hans.verkuil@cisco.com>
Acked-by: Sakari Ailus <sakari.ailus@linux.intel.com>
Signed-off-by: Hans Verkuil <hans.verkuil@cisco.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab+samsung@kernel.org>