dt-bindings: iio: ti,tmp117: add vcc supply binding

Add the binding to specify the vcc supply. We can't make it required
since this would break the backward compatibility.

Reviewed-by: Conor Dooley <conor.dooley@microchip.com>
Signed-off-by: Thomas Haemmerle <thomas.haemmerle@leica-geosystems.com>
Signed-off-by: Marco Felsch <m.felsch@pengutronix.de>
Link: https://lore.kernel.org/r/20240219131114.134607-1-m.felsch@pengutronix.de


Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>