sam-ba: new package with host variant only

sam-ba is a tool needed to reprogram AT91-based systems using an USB
connection or a serial port connection.

[Peter: Add upstream URL]
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>
Acked-by: Luca Ceresoli <luca@lucaceresoli.net>
Acked-by: Thomas De Schampheleire <thomas.de.schampheleire@gmail.com>
Signed-off-by: Peter Korsgaard <jacmet@sunsite.dk>