Compilation fails because of old pico-sdk

[stupich]

Old SDK is pulled as a submodule preventing from compilation because of code errors in it, nearest working version seems to be 1.5.1, also to comply with changes in tinyusb, update USB_ENDPOINT_SIZE to be a number instead of struct.

[progmem]

In tinyusb currently:

/// USB Endpoint Descriptor
typedef struct TU_ATTR_PACKED {
  uint8_t  bLength          ; // Size of this descriptor in bytes
  uint8_t  bDescriptorType  ; // ENDPOINT Descriptor Type
  uint8_t  bEndpointAddress ; // The address of the endpoint

  struct TU_ATTR_PACKED {
    uint8_t xfer  : 2;        // Control, ISO, Bulk, Interrupt
    uint8_t sync  : 2;        // None, Asynchronous, Adaptive, Synchronous
    uint8_t usage : 2;        // Data, Feedback, Implicit feedback
    uint8_t       : 2;
  } bmAttributes;

  uint16_t wMaxPacketSize   ; // Bit 10..0 : max packet size, bit 12..11 additional transaction per highspeed micro-frame
  uint8_t  bInterval        ; // Polling interval, in frames or microframes depending on the operating speed
} tusb_desc_endpoint_t;

Reviewing the blame indicates a change made 4 years ago to resolve an issue related to platform endianness. Basically, wMaxPacketSize used to be a struct, but it couldn't be guaranteed that bits 11-12 ended up in the correct location. The newer Pi Pico SDK uses a more up-to-date version of TinyUSB. In some ways this is actually a good thing since it falls in line more with what LUFA on the AVR uses, and both platforms are the same endian.

TODOs:

• Update the project to the latest Pi Pico SDK
• Modify the Pico USB declarations to replace the structs with size declarations. This appears to have worked based on Discord discussions.
• Actually test and validate everything is still working as expected.