staging:iio:trigger:bfintmr: Avoid divide by zero

If the timer frequency has not been configured yet get_gptimer_period() will
return 0. Handle this case instead of blindly dividing by the returned value.

Signed-off-by: Lars-Peter Clausen <lars@metafoo.de>
Signed-off-by: Jonathan Cameron <jic23@kernel.org>

diff --cc drivers/staging/iio/trigger/iio-trig-bfin-timer.c
Simple merge