This mode is unsupported, as the DMA controller can't do zero-padding
of samples.
Signed-off-by: Daniel Mack <zonque@gmail.com> Reported-by: Johannes Stezenbach <js@sig21.net> Signed-off-by: Mark Brown <broonie@linaro.org> Signed-off-by: Ben Hutchings <ben@decadent.org.uk>