tcpm: allow looking for role_sw device in the main node

If ports are defined in the tcpc main node, fwnode_usb_role_switch_get()
returns an error, meaning usb_role_switch_get() (which would succeed)
never gets a chance to run as port->role_sw isn't NULL, causing a
regression on devices where this is the case.

Fix this by turning the NULL check into IS_ERR_OR_NULL(), so
usb_role_switch_get() can actually run and the device get properly probed.

Fixes: 2d8713f ("tcpm: switch check for role_sw device with fw_node")
Cc: stable <stable@kernel.org>
Reviewed-by: Heikki Krogerus <heikki.krogerus@linux.intel.com>
Reviewed-by: Dragan Simic <dsimic@manjaro.org>
Signed-off-by: Arnaud Ferraris <arnaud.ferraris@collabora.com>
Link: https://patch.msgid.link/20260105-fix-ppp-power-v2-1-6924f5a41224@collabora.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

Author: a-wai

drivers/usb/typec/tcpm/tcpm.c

@@ -7890,7 +7890,7 @@ struct tcpm_port *tcpm_register_port(struct device *dev, struct tcpc_dev *tcpc)
 	port->partner_desc.identity = &port->partner_ident;
 
 	port->role_sw = fwnode_usb_role_switch_get(tcpc->fwnode);
-	if (!port->role_sw)
+	if (IS_ERR_OR_NULL(port->role_sw))
 		port->role_sw = usb_role_switch_get(port->dev);
 	if (IS_ERR(port->role_sw)) {
 		err = PTR_ERR(port->role_sw);