media: doc: media/v4l-drivers: Qualcomm Camera Subsystem - Media graph

Update the Qualcomm Camera Subsystem driver document with a media
controller pipeline graph diagram.

Signed-off-by: Todor Tomov <todor.tomov@linaro.org>
Signed-off-by: Hans Verkuil <hans.verkuil@cisco.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@s-opensource.com>