iwlwifi: Fix typo in iwl-commands.h for CCK rate bit range.

My first (minor) patch, hopefully this is correct.

Fix a typo in iwl-commands.h for CCK rates which needs 7 bits and not 4.
Signed-off-by: Daniel Wu <dyqith@gmail.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>

drivers/net/wireless/iwlwifi/iwl-commands.h

@@ -255,7 +255,7 @@ struct iwl_cmd_header {
  *        0x3)  54 Mbps
  *
  * Legacy CCK rate format for bits 7:0 (bit 8 must be "0", bit 9 "1"):
- *  3-0:   10)  1 Mbps
+ *  6-0:   10)  1 Mbps
  *         20)  2 Mbps
  *         55)  5.5 Mbps
  *        110)  11 Mbps