[ALSA] hda-intel - fix a race in dynamic power managment

codec->power_transition is supposed to be true while codec is going
to be shut off if in the mean time somebody calls snd_hda_power_up,
hda_power_work will not shut down the codec, but nether will clear
codec->power_transition, thus it stays on forever. Fix this.

Signed-off-by: Maxim Levitsky <maximlevitsky@gmail.com>
Signed-off-by: Takashi Iwai <tiwai@suse.de>
Signed-off-by: Jaroslav Kysela <perex@suse.cz>