regulator: act8865: add DT binding for property "active-semi,vsel-high"

Add a DT property "active-semi,vsel-high" to indicate the VSEL pin
is high. If this property is missing, then assume the VSEL pin is
low(0).

Signed-off-by: Wenyou Yang <wenyou.yang@atmel.com>
Reviewed-by: Ludovic Desroches <ludovic.desroches@atmel.com>
Signed-off-by: Mark Brown <broonie@kernel.org>