ALSA: mips/ad1843: Use WARN_ON() instead of BUG_ON()

BUG_ON() is rather useless for debugging as it leads to panic().
Use WARN_ON() and handle the error cases accordingly.

Signed-off-by: Takashi Iwai <tiwai@suse.de>
diff --git a/sound/mips/ad1843.c b/sound/mips/ad1843.c
index c624510..5869075 100644
--- a/sound/mips/ad1843.c
+++ b/sound/mips/ad1843.c
@@ -276,7 +276,7 @@
 		if (reg == -1)
 			reg = fp->reg;
 		else
-			BUG_ON(reg != fp->reg);
+			WARN_ON(reg != fp->reg);
 		m = ((1 << fp->nbits) - 1) << fp->lo_bit;
 		mask |= m;
 		bits |= (value << fp->lo_bit) & m;