remove unused includes

This patch removes includes that are not used. The removals were found with
include-what-you-use which checks if any of the symbols from a header is
in use.

src/core/ima-setup.c

@@ -22,10 +22,7 @@
 ***/
 
 #include <unistd.h>
-#include <stdio.h>
 #include <errno.h>
-#include <sys/types.h>
-#include <sys/stat.h>
 #include <fcntl.h>
 
 #include "ima-setup.h"