Attempt to make the sound driver recompile, at least for LINT which has

the sscape/trix driver active, which (for some reason) disables the
mpu401 driver, causing an undefined reference to mpuintr.  This was broken
with rev 1.79 (part of the PC98 nss driver commit).

sys/i386/isa/sound/soundcard.c

@@ -437,7 +437,7 @@ sndattach(struct isa_device * dev)
     if (strcmp(dname, "uart0") == 0)
 	dev->id_ointr = m6850intr;
 #endif
-#if NMPU > 0
+#if NMPU > 0 && defined(CONFIG_MIDI)
     if (strcmp(dname, "mpu") == 0)
 	dev->id_ointr = mpuintr;
 #endif