Detect GBA-via-link-cable as a separate Style.

SI_GBA (0x00040000) sits in libogc's N64-family group because it shares
the SI protocol bus, but logically it's a different device. Adds
N64_KIND_GBA + STYLE_GBA so a GBA tethered to a GameCube via the link
cable shows 'Style: GBA' on its port.

Like the mic, GBA doesn't answer cmd 0x01; we surface present=true
with all input fields zero. Per-GBA polling (e.g. for connection
status) would need its own path.

Author: RobertDaleSmith

gamecube/ppc/main.c

@@ -152,6 +152,7 @@ typedef enum {
   STYLE_WHEEL,
   STYLE_MOUSE,
   STYLE_MIC,
+  STYLE_GBA,
   STYLE_KEYBOARD,
 } pad_style_t;
 
@@ -163,6 +164,7 @@ static const char *format_style(pad_style_t s) {
   case STYLE_WHEEL:    return "Wheel   ";
   case STYLE_MOUSE:    return "Mouse   ";
   case STYLE_MIC:      return "Mic     ";
+  case STYLE_GBA:      return "GBA     ";
   case STYLE_KEYBOARD: return "Keyboard";
   default:             return "None    ";
   }
@@ -285,6 +287,7 @@ static void snap_n64(pad_snap_t *out, int chan, const N64State *s) {
   switch (s->kind) {
   case N64_KIND_MOUSE: out->style = STYLE_MOUSE; break;
   case N64_KIND_MIC:   out->style = STYLE_MIC;   break;
+  case N64_KIND_GBA:   out->style = STYLE_GBA;   break;
   default:             out->style = STYLE_N64;   break;
   }
   switch (s->pak) {

gamecube/ppc/n64.c

@@ -15,6 +15,7 @@
 #define N64_TYPE_CONTROLLER 0x05000000
 #define N64_TYPE_MOUSE      0x02000000
 #define N64_TYPE_MIC        0x00010000
+#define N64_TYPE_GBA        0x00040000
 
 #define PAK_ADDR_LABEL  0x0000
 #define PAK_ADDR_PROBE  0x8000
@@ -274,6 +275,7 @@ static n64_kind_t kind_for_type(u32 raw) {
   if (hi == N64_TYPE_CONTROLLER) return N64_KIND_CONTROLLER;
   if (hi == N64_TYPE_MOUSE)      return N64_KIND_MOUSE;
   if (hi == N64_TYPE_MIC)        return N64_KIND_MIC;
+  if (hi == N64_TYPE_GBA)        return N64_KIND_GBA;
   return N64_KIND_NONE;
 }
 

gamecube/ppc/n64.h

@@ -25,6 +25,7 @@ typedef enum {
   N64_KIND_CONTROLLER,
   N64_KIND_MOUSE,
   N64_KIND_MIC,
+  N64_KIND_GBA,         // GBA connected via link cable
 } n64_kind_t;
 
 typedef enum {