mfd: Convert Intel MSIC driver to use devm_* interfaces.

The devm_* functions eliminate the need for manual resource releasing
and simplify error handling. Resources allocated by devm_* are freed
automatically on driver detach.

Signed-off-by: Pasi Savanainen <ext-pasi.m.savanainen@gmail.com>
Acked-by: Mika Westerberg <mika.westerberg@linux.intel.com>
Signed-off-by: Samuel Ortiz <sameo@linux.intel.com>