mx53loco: Fix PMIC name
commit c73368150 (pmic: Extend PMIC framework to support multiple instances
of PMIC devices) has incorrectly passed the PMIC name under the FSL PMIC case.
Fix that by passing "FSL_PMIC" as the parameter of pmic_get.
Signed-off-by: Fabio Estevam <fabio.estevam@freescale.com>