mfd: intel_soc_pmic_mrfld: Convert to use new SCU IPC API

This converts the Intel Merrifield PMIC driver over the new SCU IPC API
where the SCU IPC instance is passed to the functions.

Signed-off-by: Mika Westerberg <mika.westerberg@linux.intel.com>
Reviewed-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Signed-off-by: Lee Jones <lee.jones@linaro.org>