iwlwifi: mvm: add debugfs hook to send ECHO_CMD to the firmware

ECHO_CMD is a simple command that can be sent to the
firmware just to check that it is alive.
This command is useful for debug purpose, provide a debugfs
hook to send it.

Signed-off-by: Emmanuel Grumbach <emmanuel.grumbach@intel.com>
Signed-off-by: Luciano Coelho <luciano.coelho@intel.com>
diff --git a/drivers/net/wireless/iwlwifi/mvm/fw-api.h b/drivers/net/wireless/iwlwifi/mvm/fw-api.h
index 4af7513a..cd293d2 100644
--- a/drivers/net/wireless/iwlwifi/mvm/fw-api.h
+++ b/drivers/net/wireless/iwlwifi/mvm/fw-api.h
@@ -100,6 +100,7 @@
 enum {
 	MVM_ALIVE = 0x1,
 	REPLY_ERROR = 0x2,
+	ECHO_CMD = 0x3,
 
 	INIT_COMPLETE_NOTIF = 0x4,