Actually implement the coin mech in BIO2 based games

Properly fixes #45

src/main/bio2/bi2a-iidx.h

@@ -39,7 +39,7 @@ struct bi2a_iidx_state_out {
     uint8_t UNK2;
     struct bi2a_iidx_slider SLIDER4;
     struct bi2a_iidx_slider SLIDER5;
-    uint8_t UNK3; // coin mech?
+    uint8_t coins; // coin mech?
     struct bi2a_iidx_panel PANEL;
     uint8_t UNK4;
     uint8_t UNK5;

src/main/bio2/bi2a-sdvx.h

@@ -36,7 +36,7 @@ struct bi2a_sdvx_state_in {
         uint16_t raw[8];
         struct {
             struct bi2a_sdvx_analog analogs[4];
-            uint8_t unk_1; // coin mech?
+            uint8_t coins;
             struct bi2a_sdvx_buttons1 buttons_1;
             struct bi2a_sdvx_buttons2 buttons_2;
             uint8_t unk_2[5];