staging: wilc1000: handle key related cfg operation from cfg80211 context

Refactor add/delete key operation to handle directly from cfg80211
context. Also, avoid an extra copy of the information in hif layer and
directly fill the buffer in firmware format.

Signed-off-by: Ajay Singh <ajay.kathat@microchip.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>