dt-bindings: regulator: ti,tps65132: document VIN supply

TPS65132 is powered by its VIN supply, document it.

Signed-off-by: Stanislav Jakubek <stano.jakubek@gmail.com>
Acked-by: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>
Link: https://patch.msgid.link/ZoWxnEY944ht2EWf@standask-GA-A55M-S2HP


Signed-off-by: Mark Brown <broonie@kernel.org>