regulator: mc13892: Fix voltage unit in test case.

Voltage values should be expressed in microvolts, not in milivolts.

Signed-off-by: Fabio Estevam <fabio.estevam@freescale.com>
Signed-off-by: Ranjani Vaidyanathan <ra5478@freescale.com>
Acked-by: Mark Brown <broonie@opensource.wolfsonmicro.com>
Signed-off-by: Liam Girdwood <lrg@slimlogic.co.uk>