util: Hide timespec_passed on Windows

Windows doesn't have clockid_t.

Reviewed-by: Samuel Pitoiset <samuel.pitoiset@gmail.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/7119>
diff --git a/src/util/timespec.h b/src/util/timespec.h
index cbfcc73..465adec 100644
--- a/src/util/timespec.h
+++ b/src/util/timespec.h
@@ -312,6 +312,7 @@
       (a->tv_sec > b->tv_sec);
 }
 
+#ifndef _WIN32
 /**
  * Checks whether a timespec value is after the current time
  *
@@ -326,5 +327,6 @@
    clock_gettime(clock_domain, &current_time);
    return timespec_after(&current_time, deadline);
 }
+#endif
 
 #endif /* TIMESPEC_H */