iio: event_monitor: add pitch, yaw and roll modifiers

Following the introduction of pitch, yaw and roll IIO modifiers, update the
event_monitor tool accordingly.

Signed-off-by: Andrea Merello <andrea.merello@iit.it>
Reviewed-by: Andy Shevchenko <andy.shevchenko@gmail.com>
Link: https://lore.kernel.org/r/20220907132205.28021-7-andrea.merello@iit.it


Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>