media: camss: Enable building

Add Makefile and update platform/Kconfig and platform/Makefile
to enable building of the QCom CAMSS driver.

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>