northbridge/intel/gm45: transation away from device_t

Replace the use of the old device_t definition inside
northbridge/intel/gm45.

The patch has been tested both with the arch/io.h definition of device_t
enabled and disabled in order to ensure compatibility while the
transaction takes place.

Change-Id: I87754799f922cf241fb456071bac04e6fe1eab34
Signed-off-by: Antonello Dettori <dev@dettori.io>
Reviewed-on: https://review.coreboot.org/16402
Tested-by: build bot (Jenkins)
Reviewed-by: Martin Roth <martinroth@google.com>
diff --git a/src/northbridge/intel/gm45/gm45.h b/src/northbridge/intel/gm45/gm45.h
index c018321..5a30f87 100644
--- a/src/northbridge/intel/gm45/gm45.h
+++ b/src/northbridge/intel/gm45/gm45.h
@@ -434,7 +434,7 @@
 
 void init_iommu(void);
 
-#if ENV_RAMSTAGE
+#if ENV_RAMSTAGE && !defined(__SIMPLE_DEVICE__)
 #include <device/device.h>
 
 struct acpi_rsdp;