ch552: Add USB HID and protocol support over UART

- Add USB HID support.
- Introduce a small protocol to distinguish between CDC and HID data
  sent over the UART.
- Add some debug printing.
- Cleanup of code and formatting.

hw/usb_interface/ch552_fw/include/mem.h

@@ -0,0 +1,32 @@
+#ifndef __MEM_PART_H__
+#define __MEM_PART_H__
+
+// https://github.com/contiki-os/contiki/wiki/8051-Memory-Spaces
+
+#ifdef BUILD_CODE
+#define IDATA  __idata
+#define XDATA  __xdata
+#define AT0000 __at(0x0000) // 0x000   0
+#define AT0008 __at(0x0008) // 0x008,  8
+#define AT0010 __at(0x0010) // 0x010, 16
+#define AT0040 __at(0x0040) // 0x040, 64
+#define AT0050 __at(0x0050) // 0x050, 80
+#define AT0080 __at(0x0080) // 0x080, 128
+#define AT0090 __at(0x0090) // 0x090, 144
+#define AT0100 __at(0x0100) // 0x100, 256
+#define FLASH  __code
+#else
+#define IDATA
+#define XDATA
+#define AT0000
+#define AT0008
+#define AT0010
+#define AT0040
+#define AT0050
+#define AT0080
+#define AT0090
+#define AT0100
+#define FLASH
+#endif
+
+#endif