ASoC: codec tlv320aic23 fix bogus divide by 0 message

Some code analyzer software mistakenly gives
divide by 0 error messages for these lines.
This patch will end its confusion.

Signed-off-by: Troy Kisky <troy.kisky@boundarydevices.com>
Signed-off-by: Mark Brown <broonie@opensource.wolfsonmicro.com>