ASoC: Remove unneeded !! operations while checking return value of nuc900_checkready

I think this unneededd !! operations just reduce the readability.

Signed-off-by: Axel Lin <axel.lin@gmail.com>
Acked-by: Liam Girdwood <lrg@slimlogic.co.uk>
Signed-off-by: Mark Brown <broonie@opensource.wolfsonmicro.com>