[ALSA] snd-bt87x: Make the load_all option work correctly

If the load_all option was turned on all cards would be treated as unknown,
even those which are in the database.  Of course, if the card is in the
database there is no reason to use the load_all option.  It's there to force
loading when the card isn't in the database.  But there are out of date wikis
that say to do this and some distros might turn this option on by default.
So, we keep the load_all option from turning known cards into unknown cards.

Signed-off-by: Trent Piepho <xyzzy@speakeasy.org>
Signed-off-by: Takashi Iwai <tiwai@suse.de>
Signed-off-by: Jaroslav Kysela <perex@perex.cz>