iwlwifi: mvm: add trigger for firmware dump upon statistics

It can be very useful to monitor the statistics and trigger
a firmware dump when a certain value hits a certain offset.
Since the statistics are huge, add a generic trigger. When
the DWORD at offset X reaches value Y.

Since there is another trigger before this one I can't add
right now because of a dependency on mac80211, add a
reserved entry to keep the enum in place.

Signed-off-by: Emmanuel Grumbach <emmanuel.grumbach@intel.com>