This adds support for the GRLIB APBUART UART peripheral commonly used in
LEON3/4/5 systems.
Driver features:
- Auto-detecting debug FIFO, if configured by GRMON
- Setting and getting UART transfer attributes
- Hardware FIFO if available
- Any number of APBUART devices based on devicetree
- Error status indication
- Polled operation
Signed-off-by: Martin Åberg <martin.aberg@gaisler.com>
