regulator: anatop-regulator: Remove unneeded kstrdup()

We can simply pass the regulator name via of_get_property() instead of making
a copy via kstrdup().

This leads to some code simplification.

Suggested-by: Dmitry Torokhov <dmitry.torokhov@gmail.com>
Signed-off-by: Fabio Estevam <fabio.estevam@freescale.com>
Signed-off-by: Mark Brown <broonie@linaro.org>