usb: typec: Don't prevent using constant typec_mode_desc initializers

In some situations, e.g. when registering alternate modes for local typec
ports, it may be handy to use constant mode descriptors. Allow this by
changing the mode descriptor arguments of typec_port_register_altmode()
et.al. to using const pointers.

Signed-off-by: Mats Karrman <mats.dev.list@gmail.com>
Reviewed-by: Guenter Roeck <groeck@chromium.org>
Acked-by: Heikki Krogerus <heikki.krogerus@linux.intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>