ALSA: hwdep: Don't embed device

Like control and PCM devices, it's better to avoid the embedded struct
device for hwdep (although it's more or less well working), too.
Change it to allocate via snd_device_alloc(), and free the memory at
the common snd_hwdep_free().

Reviewed-by: Jaroslav Kysela <perex@perex.cz>
Signed-off-by: Curtis Malainey <cujomalainey@chromium.org>
Tested-by: Curtis Malainey <cujomalainey@chromium.org>
Link: https://lore.kernel.org/r/20230816160252.23396-5-tiwai@suse.de


Signed-off-by: Takashi Iwai <tiwai@suse.de>