snd-fm801: autodetect SF64-PCR (tuner-only) card

When primary AC97 is not found, don't fail with tons of AC97 errors.
Assume that the card is SF64-PCR (tuner-only).
This makes the SF64-PCR radio card work "out of the box".

Also fixes a bug that can cause an oops here:
        if (tea575x_tuner > 0 && (tea575x_tuner & 0x000f) < 4) {
when tea575x_tuner == 16, it passes this check and causes problems
a couple lines below:
        chip->tea.ops = &snd_fm801_tea_ops[(tea575x_tuner & 0x000f) - 1];

Tested with SF64-PCR, but I don't have any of those sound or sound+radio cards
to test if I didn't break anything.

Signed-off-by: Ondrej Zary <linux@rainbow-software.org>
Signed-off-by: Takashi Iwai <tiwai@suse.de>