regulator: pass device_node to of_get_regulator_init_data()

It's not always true that the device_node of regulator can be found
at dev->of_node at the time when of_get_regulator_init_data() is being
called, because in some cases the regulator nodes in device tree do
not have 'struct device' behind them until regulator_dev gets created
for it by core function regulator_register().

The patch adds device_node as a new parameter to
of_get_regulator_init_data(), so that caller can pass in the node of
regulator directly.

Signed-off-by: Shawn Guo <shawn.guo@linaro.org>
Cc: Mark Brown <broonie@opensource.wolfsonmicro.com>
Cc: Liam Girdwood <lrg@ti.com>
Signed-off-by: Mark Brown <broonie@opensource.wolfsonmicro.com>