Speaking of 802.11n rates in terms of Mbps doesn't really developers
and is just useful for users. To aid debugging add the MCS index back
and an HT20/HT40 mode.

New screenshot:

    HT    MCS   Rate    Success    Retries   XRetries        PER
                6.0:          0          0          0          0
                9.0:          0          0          0          0
               12.0:         26        260          0         49
               18.0:         80        804          2         58
               24.0:          0          0          0          0
               36.0:          0          0          0          0
               48.0:          0          0          0          0
               54.0:          0          0          0          0
  HT20      0   6.5:       1368      13660          0         48
  HT20      1  13.0:          0          0          0          0
  HT20      2  19.5:          0          0          0          0
  HT20      3  26.0:          0          0          0          0
  HT20      4  39.0:          0          0          0          0
  HT20      5  52.0:         55        578         14         43
  HT20      6  58.5:         29        306          8         69
  HT20      7  65.0:         21        210          0         67
  HT20      8  13.0:         21        210          0         56
  HT20      9  26.0:          0          0          0          0
  HT20     10  39.0:          0          0          0          0
  HT20     11  52.0:          0          0          0          0
  HT20     12  78.0:          0          0          0          0
  HT20     13 104.0:          0          0          0          0
  HT20     14 117.0:          0          0          0          0
  HT20     15 130.0:         27        290         10         55
  HT40      0  13.5:         79        687         16         17
  HT40      1  27.5:         60        409         10         17
  HT40      2  40.5:         56        381         21         25
  HT40      3  54.0:         44        302         21         18
  HT40      4  81.5:         19        171          2         14
  HT40      5 108.0:          0          0          0          0
  HT40      6 121.5:          0          0          0          0
  HT40      7 135.0:          0          0          0          0
  HT40      7 150.0:          0          0          0          0
  HT40      8  27.0:          0          0          0          0
  HT40      9  54.0:          0          0          0          0
  HT40     10  81.0:          0          0          0          0
  HT40     11 108.0:         11        100          0         18
  HT40     12 162.0:         23        200          0         22
  HT40     13 216.0:         61        580          0         35
  HT40     14 243.0:         37        271          0         66
  HT40     15 270.0:         65        217          2         73
  HT40     15 300.0:          0          0          0          0

Signed-off-by: Luis R. Rodriguez <lrodriguez@atheros.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>