tock: Migrate to using an opentitan UART driver

This brings in the uart driver from lowrisc::uart, but updates it to
use offsets from the opentitan-upstream tree in an effort to get us
off the old tree.

Bug: 228243751
Change-Id: If3b9ce99ee107303d37de46dee591f120577be34
7 files changed
tree: 94be86c61180c2d47fc965bc6517fa1f1e867089
  1. app/
  2. blob_fs/
  3. capsules/
  4. chips/
  5. config/
  6. hal/
  7. platform/
  8. utils/
  9. .gitignore
  10. matcha.code-workspace