iw: add MCS set parsing
iw: add MCS set parsing

This adds MCS set parsing to iw. When you can 'iw list' you can
now see the MCS set actually parsed, this can tell you information
such as all the RX/TX MCS indexes supported, max TX spatial streams,
if TX unequal modulation is supported and your max supported HT
RX data rate.

This is as per 802.11n Draft 7 on section 7.3.2.57.4 Supported MCS Set field.

Signed-off-by: Luis R. Rodriguez <79e6b8107a8aa3944e09fad43634662ac3b91a0b@atheros.com>

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