src: Add missing include <stdlib.h>

Change-Id: I17dc2fed6c6518daf5af286788c98c049088911e
Signed-off-by: Elyes HAOUAS <ehaouas@noos.fr>
Reviewed-on: https://review.coreboot.org/c/coreboot/+/37366
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Werner Zeh <werner.zeh@siemens.com>
diff --git a/src/mainboard/sifive/hifive-unleashed/fixup_fdt.c b/src/mainboard/sifive/hifive-unleashed/fixup_fdt.c
index 8ac6ff1..3d43181 100644
--- a/src/mainboard/sifive/hifive-unleashed/fixup_fdt.c
+++ b/src/mainboard/sifive/hifive-unleashed/fixup_fdt.c
@@ -14,6 +14,7 @@
  */
 
 #include <stdint.h>
+#include <stdlib.h>
 #include <string.h>
 #include <console/console.h>
 #include <soc/otp.h>