In a function snd_pcm_hw_params_choose(), target parameters are arranged
into a table. Though each entry of this table is read-only, they don't
have const qualifier.

This commit adds the qualifier.
Signed-off-by: NTakashi Sakamoto <o-takashi@sakamocchi.jp>
Signed-off-by: NTakashi Iwai <tiwai@suse.de>