commit d7a9134 breaks boot source detection
for pcm049. The tracing vectors shows all tested boot sources, so order is
important. By not returning but overwriting src we effectively reversed the
order if more than one flag is set.

Signed-off-by: Jan Weitzel <j.weitzel@phytec.de>
Signed-off-by: Sascha Hauer <s.hauer@pengutronix.de>