ALSA: hda/ca0132 - Fix superfluous unsigned check

Fix a warning by smatch,
 sound/pci/hda/patch_ca0132.c:714 dspio_send() warn: always true
 condition '(res >= 0) => (0-u32max >= 0)'

Reported-by: Dan Carpenter <dan.carpenter@oracle.com>
Signed-off-by: Takashi Iwai <tiwai@suse.de>