iwlwifi: use a macro for default probe length

Instead of assigning the default max probe length to 200 in the main
code, create a macro for consistency and clarity.

Signed-off-by: Luciano Coelho <luciano.coelho@intel.com>
Signed-off-by: Johannes Berg <johannes.berg@intel.com>

diff --cc drivers/net/wireless/iwlwifi/iwl-drv.c
Simple merge

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