src: Use 'stdint.h' when appropriate

Change-Id: I1df255d55b8f43a711d836c2565c367bd988098a
Signed-off-by: Elyes HAOUAS <ehaouas@noos.fr>
Reviewed-on: https://review.coreboot.org/c/coreboot/+/60549
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Angel Pons <th3fanbus@gmail.com>

src/northbridge/intel/gm45/early_init.c

@@ -1,6 +1,5 @@
 /* SPDX-License-Identifier: GPL-2.0-only */
 
-#include <stdint.h>
 #include <device/pci_ops.h>
 #include <southbridge/intel/i82801ix/i82801ix.h>
 #include "gm45.h"