trivial: headers: include two files more

1- wrc.h now includes syscon.h. This is a prerequisite to a non-inline
implementation of usleep (the current inline one is just a random
loop, 10x wrong on the spec). Without this we should modify sockitowm
where it calls usleep, but I'd better not touch sockitowm.

2- syscon.h includes <sys/types.h>.  This is needed to have
useconds_t.  I'd better have usleep take unsigned long, but some file
already includes sys/types.h, so our prototype must match that one.

Signed-off-by: Alessandro Rubini <rubini@gnudd.com>

include/syscon.h

@@ -2,6 +2,7 @@
 #define __SYSCON_H
 
 #include <inttypes.h>
+#include <sys/types.h>
 
 #include "board.h"
 #undef PACKED /* if we already included a regs file, we'd get a warning */

include/wrc.h

@@ -8,6 +8,7 @@
  * Also, this brings in very common and needed headers
  */
 #include <inttypes.h>
+#include <syscon.h>
 #include <pp-printf.h>
 #define mprintf pp_printf
 #define vprintf pp_vprintf