staging: iio: remove duplicate case labels

Otherwise, compiling iio_event_monitor program fails:

io_event_monitor.c: In function ‘event_is_known’:
iio_event_monitor.c:125:2: error: duplicate case value
  case IIO_MOD_LIGHT_BOTH:
  ^
iio_event_monitor.c:121:2: error: previously used here
  case IIO_MOD_LIGHT_BOTH:

Fixes: da4db940 (iio staging: add recently added modifiers to iio_event_monitor)
Signed-off-by: Daniel Baluta <daniel.baluta@intel.com>
Signed-off-by: Jonathan Cameron <jic23@kernel.org>

drivers/staging/iio/Documentation/iio_event_monitor.c

@@ -122,8 +122,6 @@ static bool event_is_known(struct iio_event_data *event)
 	case IIO_MOD_LIGHT_IR:
 	case IIO_MOD_ROOT_SUM_SQUARED_X_Y:
 	case IIO_MOD_SUM_SQUARED_X_Y_Z:
-	case IIO_MOD_LIGHT_BOTH:
-	case IIO_MOD_LIGHT_IR:
 	case IIO_MOD_LIGHT_CLEAR:
 	case IIO_MOD_LIGHT_RED:
 	case IIO_MOD_LIGHT_GREEN: