ALSA: hdspm - Simplify with snd_pcm_hw_constraint_pow2()

Refactoring the code using snd_pcm_hw_constraint_pow2() helper function.

Tested-by: Adrian Knoth <adi@drcomp.erfurt.thur.de>
Signed-off-by: Takashi Iwai <tiwai@suse.de>