usb: typec: Add typec_port_register_altmodes()

This can be used by Type-C controller drivers which use a standard
usb-connector fwnode, with altmodes sub-node, to describe the available
altmodes.

Note there are is no devicetree bindings documentation for the altmodes
node, this is deliberate. ATM the fwnodes used to register the altmodes
are only used internally to pass platform info from a drivers/platform/x86
driver to the type-c subsystem.

When a devicetree user of this functionally comes up and the dt-bindings
have been hashed out the internal use can be adjusted to match the
dt-bindings.

Currently the typec_port_register_altmodes() function expects
an "altmodes" child fwnode on port->dev with this "altmodes" fwnode having
child fwnodes itself with each child containing 2 integer properties:

1. A "svid" property, which sets the id of the altmode, e.g. displayport
altmode has a svid of 0xff01.

2. A "vdo" property, typically used as a bitmask describing the
capabilities of the altmode, the bits in the vdo are specified in the
specification of the altmode.

Reviewed-by: Heikki Krogerus <heikki.krogerus@linux.intel.com>
Signed-off-by: Hans de Goede <hdegoede@redhat.com>
Link: https://lore.kernel.org/r/20210409134033.105834-2-hdegoede@redhat.com


Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>