docker: add debian/powerpc based on Jessie

Signed-off-by: Philippe Mathieu-Daudé <f4bug@amsat.org>
Reviewed-by: Alex Bennée <alex.bennee@linaro.org>
[AJB: split from merged patch]
Signed-off-by: Alex Bennée <alex.bennee@linaro.org>
2 files changed