staging: typec: tcpm: Respond to Discover Identity commands

If the lower level driver provided a list of VDOs in its configuration
data, send it to the partner as response to a Discover Identity command
if in device mode (UFP).

Cc: Yueyao Zhu <yueyao.zhu@gmail.com>
Originally-from: Puma Hsu <puma_hsu@htc.com>
Signed-off-by: Guenter Roeck <linux@roeck-us.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>