vendorcode/cavium/bdk/libbdk-hal: Add missing <stdlib.h>

Change-Id: Id52603c525cce1bead423d188e23f6efd50511a9
Signed-off-by: Elyes HAOUAS <ehaouas@noos.fr>
Reviewed-on: https://review.coreboot.org/c/coreboot/+/37377
Reviewed-by: Kyösti Mälkki <kyosti.malkki@gmail.com>
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>

src/vendorcode/cavium/bdk/libbdk-hal/bdk-config.c

@@ -12,6 +12,7 @@
 
 #include <bdk.h>
 #include <libbdk-hal/bdk-config.h>
+#include <stdlib.h>
 #include <string.h>
 #include <assert.h>
 #include <lame_string.h>