driver core: Use device's fwnode to check if it is waiting for suppliers

To check if a device is still waiting for its supplier devices to be
added, we used to check if the devices is in a global
waiting_for_suppliers list. Since the global list will be deleted in
subsequent patches, this patch stops using this check.

Instead, this patch uses a more device specific check. It checks if the
device's fwnode has any fwnode links that haven't been converted to
device links yet.

Signed-off-by: Saravana Kannan <saravanak@google.com>
Link: https://lore.kernel.org/r/20201121020232.908850-14-saravanak@google.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>