SDL_DelayNS() will attempt to sleep exactly the requested amount of time

This provides a highly accurate sleep function for your application, although you are still subject to being switched out occasionally.

Fixes https://github.com/libsdl-org/SDL/issues/10210

src/timer/ps2/SDL_systimer.c

@@ -39,7 +39,7 @@ Uint64 SDL_GetPerformanceFrequency(void)
     return kBUSCLK;
 }
 
-void SDL_DelayNS(Uint64 ns)
+void SDL_SYS_DelayNS(Uint64 ns)
 {
     struct timespec tv;
     tv.tv_sec = (ns / SDL_NS_PER_SECOND);