ogc: Fix timer precision (#89)

SDL_GetPerformanceCounter is supposed to return the value of a high
precision counter, but SDL_GetTicks64 returns a truncated value in
milliseconds.
Correctly return gettime() as a high precision counter instead, and
update SDL_GetPerformanceFrequency accordingly.

Author: Mefiresu

src/timer/ogc/SDL_systimer.c

@@ -53,12 +53,12 @@ Uint64 SDL_GetTicks64(void)
 
 Uint64 SDL_GetPerformanceCounter(void)
 {
-    return SDL_GetTicks64();
+    return gettime();
 }
 
 Uint64 SDL_GetPerformanceFrequency(void)
 {
-    return 1000;
+    return secs_to_ticks(1);
 }
 
 void SDL_Delay(Uint32 ms)