x86, mrst: Change the pmic_gpio device type to IPC

In latest firmware's SFI tables, pmic_gpio has been set to
IPC type of device, so we need handle it too.

Signed-off-by: Feng Tang <feng.tang@intel.com>
Signed-off-by: Alan Cox <alan@linux.intel.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>