[ALSA] hda-codec - rewrite amp cache more generic

Rewrite the code to handle amp cache and hash tables to be more
generic.  This routine will be used by the register caches in the
next patch.

Signed-off-by: Takashi Iwai <tiwai@suse.de>
Signed-off-by: Jaroslav Kysela <perex@suse.cz>