staging: ks7010: use IW_HANDLER macro in ks_wlan_handler

This commit make use of IW_HANDLER to set wext operations
of the device. Using this, comments are not neccessary anymore
and also NULL entries so readability is clearly increased.
In order to avoid casting because of the use of a different
prototype in all related functions, those which are affected
have been updated also to make use of the  union iwreq_data
as third parameter updating code accordly.
Signed-off-by: Sergio Paracuellos <sergio.paracuellos@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>