refactor codes to support samd21 devices.

[hlyi]

Changes for this pull request:

• Move majority codes under platform/samd11 to new directory platform/samdx1 so both samd11 and samd21 devices can share common code base.
• Update samd21 to use the common code base
• Change application start address of samd21 to 8K (reserved 8K for bootloader)
• Add a few new macros
  • HAL_CONFIG_HAS_PWR_STATUS: for board with three LEDs, and use the third one for a power indicator
  • DAP_CONFIG_HAS_TMS_DIR: for board with a level shifter on TMS pad, and TMS_DIR port control the input/output direction of TMS signal
  • DAP_CONFIG_RST_ACTIVE_HIGH. When defined, nRESET will be an active high reset instead of default active low reset
  • DAP_CONFIG_HAS_RST_SENSE: When defined, the sense of nRESET will be on a different GPIO than the GPIO driver of nRESET.
  • HAL_CONFIG_CUSTOM_LED: when defined, the following functions are expected to be implmented: custom_hal_gpio_dap_status_toggle, custom_hal_gpio_dap_status_set, custom_hal_gpio_vcp_status_toggle, custom_hal_gpio_vcp_status_write, led_custom_init. Those functions provide custom behaviors of LEDs. For Jeff Probe, onboard status LEDs are too bright. the custom LED functions use PWM output to dim them
  • DAP_CONFIG_SUPPLY_PWR: when defined, a GPIO will control supplying power to the external target
• Add target for Jeff Probe: HAL_BOARD_JEFF_PROBE

[ataradov]

The goal of this repo is to distribute the basic CMSIS-DAP implementation. The platform stuff is to prove a basic example of how to use it. Those examples are provided for the hardware I can reasonably test when making changes. I don't want to maintain all the board build based on this implementation.

This makes the example more complicated, which is the opposite of my goal here.

It is fine of implementations for specific boards are maintained separately. I myself have a lot of boards that are not included here.

And as far as direction control goes - I have a much cleaner and more generic implementation in mind, I just don't have time to work on that at the moment.

[ataradov]

None of this stuff is going to be merged. I will not merge things for specific implementations.

[ataradov]

Closing this pull request.