mb/siemens: Get rid of device_t

Use of device_t has been abandoned in ramstage.

Change-Id: If67ea25a9e1363dde8aefe62b92ee7a61f0458b0
Signed-off-by: Elyes HAOUAS <ehaouas@noos.fr>
Reviewed-on: https://review.coreboot.org/26097
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Patrick Rudolph <siro@das-labor.org>
Reviewed-by: Werner Zeh <werner.zeh@siemens.com>
Reviewed-by: Mario Scheithauer <mario.scheithauer@siemens.com>
diff --git a/src/mainboard/siemens/mc_apl1/mainboard.c b/src/mainboard/siemens/mc_apl1/mainboard.c
index 09667cc..b81da5f 100644
--- a/src/mainboard/siemens/mc_apl1/mainboard.c
+++ b/src/mainboard/siemens/mc_apl1/mainboard.c
@@ -196,7 +196,7 @@
 static void mainboard_final(void *chip_info)
 {
 	uint16_t cmd = 0;
-	device_t dev = NULL;
+	struct device *dev = NULL;
 
 	/* Do board specific things */
 	variant_mainboard_final();