efikamx: Fix pmic_init() argument

On efikamx board the PMIC is connected via SPI interface, so it does not make
sense to pass I2C_PMIC into the pmic_init() interface.

Pass the SPI bus number via CONFIG_FSL_PMIC_BUS option instead.

Signed-off-by: Fabio Estevam <fabio.estevam@freescale.com>