Added some documentation for affine_background_load_palette()

include/affine_background.h

@@ -11,6 +11,7 @@
 void affine_background_init();
 void affine_background_update();
 void affine_background_set_color(COLOR color);
+// Must be called with an array of size at least  AFFINE_BG_PAL_LEN
 void affine_background_load_palette(const void *src);
 
-#endif // AFFINE_BACKGROUND_H
+#endif // AFFINE_BACKGROUND_H