feat: add MIDI 2.0 Device class driver (USB-MIDI 2.0)

Add native USB-MIDI 2.0 Device class driver to TinyUSB. Implements the
USB-MIDI 2.0 specification with both Alt Setting 0 (MIDI 1.0 fallback)
and Alt Setting 1 (UMP native) descriptor support.

Driver features:
- UMP (Universal MIDI Packet) read/write with atomic message framing
- Protocol negotiation: Endpoint Discovery, Config Request/Notify,
  Function Block Discovery (embedded in driver)
- Group Terminal Block descriptor via GET_DESCRIPTOR
- Alt Setting switch handler with endpoint re-arm
- Static allocation, no dynamic memory, ISR-safe

Build system:
- Register midi2d_* in usbd.c driver table
- Add TUD_MIDI2_DESCRIPTOR macros to usbd.h
- Add config defaults (CFG_TUD_MIDI2_*) to tusb_option.h
- Add midi2_ump_word_count() to midi.h (shared by Device and Host)
- Add midi2_device.c/h to family.cmake and CMakeLists.txt
- Add midi2_device.h include to tusb.h

All changes guarded by #if CFG_TUD_MIDI2 (default 0). Zero impact on
existing drivers and examples.

Tested: Raspberry Pi Pico (RP2040), Linux ALSA, Windows MIDI Services

1 files changed, 18 insertions, 0 deletions

diff --git a/src/class/midi/midi.h b/src/class/midi/midi.h
index cd67640e4..8121ec016 100644
--- a/src/class/midi/midi.h
+++ b/src/class/midi/midi.h
@@ -186,6 +186,24 @@ typedef midi_desc_cs_endpoint_n_t(1) midi_desc_cs_endpoint_1jack_t;
 TU_VERIFY_STATIC(sizeof(midi_desc_cs_endpoint_1jack_t) == 4+1, "size is not correct");
 
 //--------------------------------------------------------------------+
+// MIDI 2.0 UMP Helpers
+//--------------------------------------------------------------------+
+
+// Return the number of 32-bit words for a UMP message given its Message Type
+static inline uint8_t midi2_ump_word_count(uint8_t mt) {
+  switch (mt) {
+    case 0x0: case 0x1: case 0x2: case 0x6: case 0x7:
+      return 1;
+    case 0x3: case 0x4: case 0x8: case 0x9: case 0xA:
+      return 2;
+    case 0xB: case 0xC:
+      return 3;
+    default: // 0x5, 0xD, 0xE, 0xF
+      return 4;
+  }
+}
+
+//--------------------------------------------------------------------+
 // For Internal Driver Use
 //--------------------------------------------------------------------+
 typedef struct {