N3DS: Fix -Wformat warnings in tests.

All warnings were about invalid specifiers. Since U/Sint32 is a long,
using `%d` emits a -Wformat warning.

test/testvulkan.c

@@ -1101,7 +1101,7 @@ int main(int argc, char **argv)
     }
 
     SDL_GetCurrentDisplayMode(0, &mode);
-    SDL_Log("Screen BPP    : %d\n", SDL_BITSPERPIXEL(mode.format));
+    SDL_Log("Screen BPP    : %" SDL_PRIu32 "\n", SDL_BITSPERPIXEL(mode.format));
     SDL_GetWindowSize(state->windows[0], &dw, &dh);
     SDL_Log("Window Size   : %d,%d\n", dw, dh);
     SDL_Vulkan_GetDrawableSize(state->windows[0], &dw, &dh);