Slight formatting cleanup to ensure the docs are rendered and linked
properly.

Signed-off-by: Rahix <rahix@rahix.de>

See merge request !419

See merge request !414

The -EIO error was triggering a warning in the caller.

Make private functions static
Allocate buffers on stack
Move constants out of header

Pycardium Improvements

Closes #76 and #212

See merge request card10/firmware!417

This will result in more reliably reaching a clean state.

Co-Authored-By: schneider <schneider@muc.ccc.de>
Signed-off-by: Rahix <rahix@rahix.de>

See merge request !418