This was spotted by Fernando Lopez-Lezcano <nando@ccrma.Stanford.EDU>
while he tried to compile a -RT kernel with this driver enabled.
"make C=2" would also warn about this. This is is based on his patch.
Reported-by: Fernando Lopez-Lezcano <nando@ccrma.Stanford.EDU>
Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Acked-by: Vinod Koul <vinod.koul@intel.com>
Signed-off-by: Mark Brown <broonie@kernel.org>