media: cec: core: add new CEC_MSG_FL_REPLY_VENDOR_ID flag

If this flag is set, then the reply is expected to consist of
the CEC_MSG_VENDOR_COMMAND_WITH_ID opcode followed by the Vendor ID (as
used in bytes 1-4 of the message), followed by the struct cec_msg reply
field.

Note that this assumes that the byte after the Vendor ID is a
vendor-specific opcode.

This flag makes it easier to wait for replies to vendor commands,
using the same CEC framework support for waiting for regular replies.

Support for this flag is indicated by setting the new
CEC_CAP_REPLY_VENDOR_ID capability.

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