wifi: iwlwifi: mld: don't return an error if the FW is dead

wifi: iwlwifi: mld: don't return an error if the FW is dead

If iwl_mld_change_vif_links failed to add the requested link(s)
because the FW is dead (error before recovery), there is no point
in returning an error value, as the reconfig will re-add the link(s)
after the FW is started.
Return 0 in that case, and WARN in the others.

Signed-off-by: Miri Korenblit <miriam.rachel.korenblit@intel.com>
Reviewed-by: Johannes Berg <johannes.berg@intel.com>
Link: https://patch.msgid.link/20250430151952.c549c72b1f37.I445bf723e9befc9541b4abd0ec7c72db8f1ff177@changeid