drivers/ws281x: add SysTick + GPIO LL backend

[maribu]

Contribution description

This implements a new ws281x backend that is largely inspired by @chrysn's periph_timer_poll + GPIO LL backend, but uses SysTick instead of periph_timer_poll. The advantage is that the SysTick timer is provided by all Cortex M MCUs and therefore (hopefully) should work on all Cortex M MCUs.

Testing procedure

Run the tests/drivers/ws281x app on a Cortex M MCU; it should now be used as default backend on Cortex M MCUs.

I tested this successfully with

• [x] nucleo-f072rb
• [x] nucleo-f103rb
• [x] nucleo-f303re
• [x] nucleo-f446re
• [x] nucleo-g070rb

Issues/PRs references

None

[riot-ci]

Murdock results

:heavy_check_mark: PASSED

1bbce1f351eee0fdfd4fa7a3de3a6b4394c6daeb fixup! drivers/ws281x: add SysTick + GPIO LL backend

Success	Failures	Total	Runtime
10088	0	10088	13m:26s

Artifacts

• Documentation preview