ALSA: ice1724 - make some bitfields unsigned

This is a clean up and doesn't change the behavior.

Bit fields should always be unsigned.  Otherwise pm_suspend_enabled will
be -1 when you want it to be 1.  The other bad thing is that the sparse
checker will complain 36 times if they aren't unsigned.

The other bitfields in that struct are unsigned already.

Signed-off-by: Dan Carpenter <error27@gmail.com>
Signed-off-by: Takashi Iwai <tiwai@suse.de>