media: uapi: cec-funcs.h: use CEC_LOG_ADDR_BROADCAST

The cec-funcs.h header sets the destination to 0xf for those
messages that can only be broadcast. Instead of writing:

	msg->msg[0] |= 0xf; /* broadcast */

just write:

	msg->msg[0] |= CEC_LOG_ADDR_BROADCAST;

which is more descriptive and allows us to drop the comment.

Signed-off-by: Hans Verkuil <hverkuil@xs4all.nl>
Signed-off-by: Mauro Carvalho Chehab <mchehab+huawei@kernel.org>