sound: OSS: keep index within bounds of midi_devs[]

When the {orig,midi}_dev equals num_midis, that's one too
large already.
Signed-off-by: Roel Kluin <roel.kluin@gmail.com>
Signed-off-by: Takashi Iwai <tiwai@suse.de>

sound/oss/midi_synth.c

@@ -426,7 +426,7 @@ midi_synth_open(int dev, int mode)
 	int             err;
 	struct midi_input_info *inc;
 
-	if (orig_dev < 0 || orig_dev > num_midis || midi_devs[orig_dev] == NULL)
+	if (orig_dev < 0 || orig_dev >= num_midis || midi_devs[orig_dev] == NULL)
 		return -ENXIO;
 
 	midi2synth[orig_dev] = dev;

sound/oss/mpu401.c

@@ -770,7 +770,7 @@ static int mpu_synth_ioctl(int dev, unsigned int cmd, void __user *arg)
 
 	midi_dev = synth_devs[dev]->midi_dev;
 
-	if (midi_dev < 0 || midi_dev > num_midis || midi_devs[midi_dev] == NULL)
+	if (midi_dev < 0 || midi_dev >= num_midis || midi_devs[midi_dev] == NULL)
 		return -ENXIO;
 
 	devc = &dev_conf[midi_dev];