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 <[e-mail]>

sound/mips/ad1843.c

···
 		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;