soc/intel/quark: Get rid of device_t

Use of device_t has been abandoned in ramstage.

Change-Id: I102c9b9b1066064589149388d5ebbcd6d0d81fa7
Signed-off-by: Elyes HAOUAS <ehaouas@noos.fr>
Reviewed-on: https://review.coreboot.org/26542
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Patrick Rudolph <siro@das-labor.org>

src/soc/intel/quark/spi.c

@@ -232,7 +232,7 @@ void spi_init(void)
 	uint32_t bios_control;
 	struct spi_context *context;
 	volatile struct flash_ctrlr *ctrlr;
-	device_t dev;
+	struct device *dev;
 	uint32_t rcba;
 
 	/* Determine the base address of the SPI flash controller */