Slightly improve cold-boot start

Move the initial screen rendering to before doing USB/BLE init, which
should hopefully limit the amount of time until initial rendering.

src/main.c

@@ -33,7 +33,7 @@ int btn2_hold = 0;
 int image_index = 0;
 
 int frame = 0;
-int subframe = 0;
+int subframe = 99999;
 
 int main_handler(void) {
 
@@ -100,13 +100,14 @@ int main()
     TMR3_ITCfg(ENABLE, TMR0_3_IT_CYC_END);
     PFIC_EnableIRQ(TMR3_IRQn);
 
+    wang_init();
+    main_handler();
+
     usb_register_handler(bl_handler);
     usb_init();
 
     ble_init();
 
-    wang_init();
-
     while (1) {
         WWDG_SetCounter(0x7F);
         static int btldr_timer = 0;