iwinfo: fix iwinfo_hardware() return value if chip id is not found

git-svn-id: svn://svn.openwrt.org/openwrt@36471 3c298f89-4303-0410-b956-a3cf2f4a3e73
AA: iwinfo: merge r36471

git-svn-id: svn://svn.openwrt.org/openwrt@36472 3c298f89-4303-0410-b956-a3cf2f4a3e73