media: cec.h: initialize *parent and *port in cec_phys_addr_validate

Make sure these values are set to avoid 'uninitialized variable'
warnings. Hasn't happened yet, but better safe than sorry.

Signed-off-by: Hans Verkuil <hans.verkuil@cisco.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@s-opensource.com>