iwmc3200wifi: rfkill cleanup

The patch cleans up the unused rfkill related structures and flags.
It also adds wext and cfg80211 handlers for txpower auto and off so
that software rfkill could be issued by user space.

Signed-off-by: Zhu Yi <yi.zhu@intel.com>
Signed-off-by: Samuel Ortiz <samuel.ortiz@intel.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>