src/cpu: Use 'include <stdlib.h>' when appropriate

Change-Id: I44346594bc106eed73a1268b82f026b69e5f4512
Signed-off-by: Elyes HAOUAS <ehaouas@noos.fr>
Reviewed-on: https://review.coreboot.org/c/coreboot/+/32821
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Martin Roth <martinroth@google.com>

src/cpu/amd/family_10h-family_15h/init_cpus.h

@@ -16,7 +16,6 @@
 #ifndef INIT_CPUS_H
 #define INIT_CPUS_H
 
-#include <stdlib.h>
 #include <cpu/x86/lapic.h>
 #include <cpu/x86/mtrr.h>
 #include <cpu/amd/msr.h>