[ALSA] SOC: fix tests in cs4270_hw_params()

cs4270_hw_params does several times:

ret = snd_soc_write()
if (ret < 0)
	...

This only works when ret is signed.

Signed-off-by: Roel Kluin <12o3l@tiscali.nl>
Signed-off-by: Takashi Iwai <tiwai@suse.de>