mb/kontron/mal10: Use the system library for headers

Use the system library for header files instead of relative filesystem
paths.

Built with BUILD_TIMELESS=1, coreboot.rom remains the same.

Signed-off-by: Felix Singer <felixsinger@posteo.net>
Change-Id: I0b356d0188f104d7c49571ce5c8fe65e79589123
Reviewed-on: https://review.coreboot.org/c/coreboot/+/48141
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Frans Hendriks <fhendriks@eltan.com>

src/mainboard/kontron/mal10/carriers/t10-tni/gpio.c

@@ -1,6 +1,6 @@
 /* SPDX-License-Identifier: GPL-2.0-only */
 
-#include "include/carrier/gpio.h"
+#include <carrier/gpio.h>
 
 static const struct pad_config gpio_table[] = {
 	PAD_CFG_GPIO_DRIVER_HI_Z(GPIO_0, DN_20K, DEEP, IGNORE, SAME),

src/mainboard/kontron/mal10/variants/mal10/gpio.c

@@ -1,6 +1,6 @@
 /* SPDX-License-Identifier: GPL-2.0-only */
 
-#include "include/variant/gpio.h"
+#include <variant/gpio.h>
 
 static const struct pad_config gpio_table[] = {
 	/* SPI */