ACPI: property: Rework acpi_graph_get_next_endpoint()

ACPI: property: Rework acpi_graph_get_next_endpoint()

Rework the code obtaining the next endpoint in
acpi_graph_get_next_endpoint(). The resulting code removes unnecessary
contitionals and should be easier to follow.

Suggested-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Signed-off-by: Sakari Ailus <sakari.ailus@linux.intel.com>
Reviewed-by: Laurent Pinchart <laurent.pinchart+renesas@ideasonboard.com>
Link: https://patch.msgid.link/20251001104320.1272752-4-sakari.ailus@linux.intel.com
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>