regulator: palmas: get regulators node from parent node only

The device tree binding of Palmas regulator driver says as:

palmas_pmis {
	compatible = "ti,palmas-pmic";
	...
	regulators {
		...
	}
};

In this "regulators" subnode is expected to be part of parent node, not
the outside of parent node. Hence to get the regulator node, the correct
call is of_get_child_by_name() rather than of_find_node_by_name() which
actually searches the "regulators" node from the parent node to end of DTS
file.

Signed-off-by: Laxman Dewangan <ldewangan@nvidia.com>
Reviewed-by: Stephen Warren <swarren@nvidia.com>
Signed-off-by: Mark Brown <broonie@linaro.org>