board: Add support for Conclusive KSTR-SAMA5D27

Introduce support for Conclusive KSTR-SAMA5D27 Single Board Computer.

Co-developed-by: Jakub Klama <jakub@conclusive.pl>
Signed-off-by: Jakub Klama <jakub@conclusive.pl>
Co-developed-by: Marcin Jabrzyk <marcin@conclusive.pl>
Signed-off-by: Marcin Jabrzyk <marcin@conclusive.pl>
Signed-off-by: Artur Rojek <artur@conclusive.pl>