linux-phytec-fsl

airo: prevent potential underflow in airo_set_freq()

I'm not sure if this can underflow but Smatch complains.  It seems
harmless to add a check for negatives.

Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>
Signed-off-by: Kalle Valo <kvalo@codeaurora.org>