staging: ks7010: Factor out repeated code into function 'ks_wlan_cap()'.

The code that generates a WLAN capability mask is repeated in five
functions.  This change refactors that code into a new function, which is
called now in each of those functions.

Signed-off-by: Quytelda Kahja <quytelda@tamalin.org>
Reviewed-by: Tobin C. Harding <me@tobin.cc>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>