mac_addr_n2a: don't use an unused 'blen' variable
mac_addr_n2a: don't use an unused 'blen' variable

OSLL/iw,OSLL/iw,TeamEOS/external_iw,Distrotech/iw,CTU-IIG/802.11p-iw,idor/iw,chunyeow/iw,bw-oss/iw,SoluMachines/external_iw,bcopeland/android_iw,SoluMachines/external_iw,ewa/iw-modified,bw-oss/iw,TeamEOS/external_iw,cozybit/iw,greearb/iw-ct,chunyeow/iw,ewa/iw-modified,CTU-IIG/802.11p-iw,greearb/iw-ct,Distrotech/iw,idor/iw,timduru/platform-external-iw,timduru/platform-external-iw,cozybit/iw,bcopeland/android_iw