regulator: tps65090: Fix tps65090 typos in example

Specification and existing device trees use vsys-l{1,2}-supply,
not vsys_l{1,2}-supply. Fix the example to match the specification.

Fixes: 21d2202158 ("mfd: tps65090: add DT support for tps65090")
Reviewed-by: Doug Anderson <dianders@chromium.org>
Acked-by: Mark Rutland <mark.rutland@arm.com>
Signed-off-by: Andreas Färber <afaerber@suse.de>
Reviewed-by: Javier Martinez Canillas <javier.martinez@collabora.co.uk>
Signed-off-by: Mark Brown <broonie@linaro.org>

Documentation/devicetree/bindings/regulator/tps65090.txt

@@ -45,8 +45,8 @@ Example:
 		infet5-supply = <&some_reg>;
 		infet6-supply = <&some_reg>;
 		infet7-supply = <&some_reg>;
-		vsys_l1-supply = <&some_reg>;
-		vsys_l2-supply = <&some_reg>;
+		vsys-l1-supply = <&some_reg>;
+		vsys-l2-supply = <&some_reg>;
 
 		regulators {
 			dcdc1 {