share/examples/sound: Fix spelling "controller"

Event:		Advanced UNIX Programming Course (Fall’23) at NTHU.
Pull Request:	https://github.com/freebsd/freebsd-src/pull/994

share/examples/sound/midi.c

@@ -49,7 +49,7 @@ main()
 		switch (event.type) {
 		case NOTE_ON:
 		case NOTE_OFF:
-		case CONTROLER_ON:
+		case CONTROLLER_ON:
 			if ((l = read(midi_config.fd, &(event.note), sizeof(event.note))) == -1) {
 				perror("Error reading MIDI note");
 				exit(1);
@@ -65,7 +65,7 @@ main()
 		case NOTE_OFF:
 			printf("Channel %d, note %d, velocity %d\n", event.channel, event.note, event.velocity);
 			break;
-		case CONTROLER_ON:
+		case CONTROLLER_ON:
 			printf("Channel %d, controller %d, value %d\n", event.channel, event.controller, event.value);
 			break;
 		default:

share/examples/sound/ossmidi.h

@@ -33,7 +33,7 @@
 #define NOTE_ON 0x90
 #define NOTE_OFF 0x80
 #define CHANNEL_MASK 0xF
-#define CONTROLER_ON 0xB0
+#define CONTROLLER_ON 0xB0
 
 typedef struct midi_event {
 	unsigned char type;