ALSA: info: Remove unused function declarations

These declarations is never used since beginning of git history.

Signed-off-by: Yue Haibing <yuehaibing@huawei.com>
Link: https://lore.kernel.org/r/20230807141513.31440-1-yuehaibing@huawei.com
Signed-off-by: Takashi Iwai <tiwai@suse.de>