iwlwifi: move content of iwl_probe to post fetch_fw

iwlwifi: move content of iwl_probe to post fetch_fw

This will allow to have different behavior depending on the fw.
Different fw APIs require completely different implementation
of the mac80211 APIs. Each of these implementations is called an
op_mode.

The current op_mode is called DVM which states for dual virtual MAC.

Signed-off-by: Emmanuel Grumbach <emmanuel.grumbach@intel.com>
Signed-off-by: Wey-Yi Guy <wey-yi.w.guy@intel.com>