wifi: iwlwifi: work around -Wenum-compare-conditional warning

wifi: iwlwifi: work around -Wenum-compare-conditional warning

This is one of only three -Wenum-compare-conditional warnings we get
in randconfig builds:

drivers/net/wireless/intel/iwlwifi/mvm/sta.c:4331:17: error: conditional expression between different enumeration types ('enum iwl_fw_sta_type' and 'enum iwl_sta_type') [-Werror,-Wenum-compare-conditional]
 4331 |         u32 type = mld ? STATION_TYPE_PEER : IWL_STA_LINK;
      |                        ^ ~~~~~~~~~~~~~~~~~   ~~~~~~~~~~~~

This is a false positive since the code works as intended, but the
warning is otherwise sensible, so slightly rewrite it in order to
not trigger the warning.

Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Link: https://patch.msgid.link/20241018151841.3821671-1-arnd@kernel.org
Signed-off-by: Johannes Berg <johannes.berg@intel.com>