The MSIC MFD driver creates platform devices for MSIC device drivers so we
don't need to create them in platform code anymore.

This patch adds a new runtime check which determines whether we are running
on a Medfield platform and enables the MSIC MFD driver accordingly.
Signed-off-by: Mika Westerberg <mika.westerberg@linux.intel.com>
Signed-off-by: Samuel Ortiz <sameo@linux.intel.com>