pmic: dialog: Avoid name conflicts

As mx53loco board has two variants: one with Dialog PMIC and another with FSL MC34708 PMIC,
we need to be able to build both drivers.

Change pmic_init() and PMIC_NUM_OF_REGS names to avoid build conflicts when both drivers are present.

Signed-off-by: Fabio Estevam <fabio.estevam@freescale.com>
Acked-by: Stefano Babic <sbabic@denx.de>