usb: typec: tcpm: Use usb_debug_root as root for our debugfs entry

usb: typec: tcpm: Use usb_debug_root as root for our debugfs entry

Use usb_debug_root as root for our debugfs entry instead of creating our
own subdirectory under the debugfs root.

Another patch in this series will make the same change to the fusb302
driver, which also uses dev_name() (on the same device) for the debugfs
entry name. So we also prefix dev_name() with "tcpm-" here to avoid a
name conflict.

Reviewed-by: Guenter Roeck <linux@roeck-us.net>
Reviewed-by: Heikki Krogerus <heikki.krogerus@linux.intel.com>
Signed-off-by: Hans de Goede <hdegoede@redhat.com>
Link: https://lore.kernel.org/r/20190817184340.64086-1-hdegoede@redhat.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>