There's a wmi event generated by dell-wmi when pressing keyboard backlight
toggle key:
[1224203.948894] dell_wmi: Unknown key with type 0x0011 and code 0x01e2 pressed

This event is for notification purposes, let's ignore it.
Signed-off-by: Rhys Kidd <rhyskidd@gmail.com>
Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>