Merge #343

343:  Add embedded_hal::serial implementation for uarte (continuation) r=jonas-schievink a=hargoniX

Since #281 has been abandoned by the author this is a continuation of his work in a seperate PR.

Co-authored-by: Ulf Lilleengen <ulf.lilleengen@gmail.com>
Co-authored-by: Henrik Böving <hargonix@gmail.com>

Author: 3 people