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/cryptsetup/cryptsetup-generator.c

@@ -20,11 +20,8 @@
 ***/
 
 #include <errno.h>
-#include <string.h>
-#include <unistd.h>
 
 #include "dropin.h"
-#include "fileio.h"
 #include "generator.h"
 #include "hashmap.h"
 #include "log.h"

src/cryptsetup/cryptsetup.c

@@ -32,7 +32,6 @@
 #include "path-util.h"
 #include "strv.h"
 #include "ask-password-api.h"
-#include "def.h"
 #include "libudev.h"
 #include "udev-util.h"