iwlwifi: mvm: add debugfs to trigger fw debug logs collection

This allows to collect the logs even if the firmware hasn't
crashed. Of course, crashing the firmware is an option, but
this is easier and nicer.

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

diff --cc drivers/net/wireless/iwlwifi/iwl-prph.h
Simple merge

diff --cc drivers/net/wireless/iwlwifi/mvm/debugfs.c
Simple merge

diff --cc drivers/net/wireless/iwlwifi/mvm/fw.c
Simple merge

diff --cc drivers/net/wireless/iwlwifi/mvm/mvm.h
Simple merge