[media] af9013: add configurable TS output pin

On serial TS mode output pin could be selected from D0 or D7.
Add configuration option to for it.

Rename TS mode config option prefix from AF9013_TS_ to AF9013_TS_MODE_.

Signed-off-by: Antti Palosaari <crope@iki.fi>
Signed-off-by: Mauro Carvalho Chehab <mchehab@s-opensource.com>