chore: move firmware to firmware/ folder

feat: vos0, system clock at 480 MHz

Revert "feat: atomic register modifications"

This reverts commit 997dd77e0476ee3929fdab6b1ad29cef85f32c2b.

feat: atomic register modifications

fix: ensure register access are inline

docs: add documentation comments to most functions

chore: some renames

feat: add registers, pin, exti, usb_device skeleton