dell-wmi: Sort WMI event codes and update comments

For better readability of keymap table, sort events by codes and also
update comments for events to be more informative.

Signed-off-by: Pali Rohár <pali.rohar@gmail.com>
Tested-by: Michał Kępień <kernel@kempniu.pl>
Reviewed-by: Michał Kępień <kernel@kempniu.pl>
Tested-by: Gabriele Mazzotta <gabriele.mzt@gmail.com>
Signed-off-by: Darren Hart <dvhart@linux.intel.com>