ALSA: jazz16: refine dma and irq selection

Narrow the dma and irq selection after the DOS driver.

Add ALSA configuration description as well.

Signed-off-by: Krzysztof Helt <krzysztof.h1@wp.pl>
Signed-off-by: Takashi Iwai <tiwai@suse.de>
diff --git a/sound/isa/sb/sb8_main.c b/sound/isa/sb/sb8_main.c
index 3222aed..7d84c9f 100644
--- a/sound/isa/sb/sb8_main.c
+++ b/sound/isa/sb/sb8_main.c
@@ -510,7 +510,8 @@
 	}
 	switch (chip->hardware) {
 	case SB_HW_JAZZ16:
-		runtime->hw.formats |= SNDRV_PCM_FMTBIT_S16_LE;
+		if (chip->dma16 == 5 || chip->dma16 == 7)
+			runtime->hw.formats |= SNDRV_PCM_FMTBIT_S16_LE;
 		runtime->hw.rates |= SNDRV_PCM_RATE_8000_48000;
 		runtime->hw.rate_min = 4000;
 		runtime->hw.rate_max = 50000;