fix compile error in prom.c

arch/mips/lantiq/grx500/prom.c

@@ -158,7 +158,7 @@ static void plat_early_init_devtree(void)
 		pr_info("Using Device tree (DTB) from bootloader %p (%p)\n", (void *)(fw_passed_dtb - 0x20000000), (void*)fw_passed_dtb);
 		fw_passed_dtb -= 0x20000000; /* KEN: compensate for the change in BASE address for the kernel. */
 #else
-		pr_info("Using Device tree (DTB) appended to kernel image %p\n", fw_passed_dtb);
+		pr_info("Using Device tree (DTB) appended to kernel image %p\n", (void *)fw_passed_dtb);
 #endif
 		dtb = (void *)fw_passed_dtb;
 	}