Just ignore ADB Service Request

- to support Adjustable keyboard(composite device?)

protocol/adb.c

@@ -128,6 +128,10 @@ uint16_t adb_host_kbd_recv(void)
     attention();
     send_byte(0x2C);            // Addr:Keyboard(0010), Cmd:Talk(11), Register0(00)
     place_bit0();               // Stopbit(0)
+    if (!wait_data_hi(500)) {    // Service Request(310us Adjustable Keyboard): just ignored
+        sei();
+        return -30;             // something wrong
+    }
     if (!wait_data_lo(500)) {   // Tlt/Stop to Start(140-260us)
         sei();
         return 0;               // No data to send