media: cec-ioc-dqevent.rst: fix typo

The documentation talked about INITIAL_VALUE when the actual define is
INITIAL_STATE.

Fix this.

Signed-off-by: Hans Verkuil <hans.verkuil@cisco.com>
Reported-by: Jonas Karlman <jonas@kwiboo.se>
Signed-off-by: Mauro Carvalho Chehab <mchehab@s-opensource.com>