regulator: palmas: Add tps65917 compatible string

Add tps65917 compatible string.

Signed-off-by: Keerthy <j-keerthy@ti.com>
Signed-off-by: Mark Brown <broonie@linaro.org>

Documentation/devicetree/bindings/regulator/palmas-pmic.txt

@@ -7,6 +7,7 @@ Required properties:
   ti,twl6037-pmic
   ti,tps65913-pmic
   ti,tps65914-pmic
+  ti,tps65917-pmic
 and also the generic series names
   ti,palmas-pmic
 - interrupt-parent : The parent interrupt controller which is palmas.