ec/acpi: Add missing include

Change-Id: I61c2191f28b6c2c9a6bc587dc3b6c2ae28205192
Signed-off-by: Nico Huber <nico.huber@secunet.com>
Reviewed-on: https://review.coreboot.org/17124
Tested-by: build bot (Jenkins)
Reviewed-by: Stefan Reinauer <stefan.reinauer@coreboot.org>

src/ec/acpi/ec.h

@@ -16,6 +16,8 @@
 #ifndef _EC_ACPI_H
 #define _EC_ACPI_H
 
+#include <stdint.h>
+
 #define EC_DATA	0x62
 #define EC_SC	0x66